Romania in World War I

Between 1914 and 1916, 59 Romanian factories produced 400,000 artillery rounds, 70 million bullets, 1,500 caissons, and 332 gun carriages. Grenades were also manufactured, with three factories producing 1.5 tons of explosives daily.[32] The 332 gun carriages were produced in order to convert Romania's 53 mm and 57 mm Fahrpanzer fortress guns into field artillery.[33] Some of the 57 mm guns were converted into anti-aircraft guns using a carriage designed by the Romanian General Ștefan Burileanu.[34] The Romanian army badly lacked arms and ammunitions during the war,[35] due to the industrial underdevelopment of the country.[36]

The Romanian Legion in Italy

In Italy, in October 1918, Romanian prisoners of war from the Austro-Hungarian Army formed the Romanian Legion of Italy (Legione Romena d'Italia), which joined the fighting during the last battles on the Italian front (Battle of Vittorio Veneto) and later, after the end of the war, participated in the Hungarian–Romanian War.

Diplomatic and political efforts to establish the Legion started in early July 1916. These efforts gained notable consistency in Italy after the "Congress of the Oppressed Nations in Austria-Hungary" was held in April 1918 in Rome, at a time when Italy became interested in further efforts to hasten the disintegration of the Austro-Hungarian state.

Following requests for enlistment to fight against Austria-Hungary, the Romanian volunteers were incorporated in July 1918 into the Italian Royal Army, to be enlisted in October of the same year in a large national unit. Between July and October 1918, three companies were formed, named "Horea", "Cloșca" and "Crișan". The equipment and endowment of the constituted units and subunits was made with Italian military equipment. Only the three companies formed prior to October 1918 actually fought until the armistice of November 3, 1918. Taking part in the battles of Vittorio Veneto, Montello, Sisemolet, Piave, Cimone and Monte Grappa.[48]

The Austro-Hungarian soldiers of Romanian origin from Transylvania, Banat, Bukovina, and Crișana were not few: it is estimated that during 1914-1918, between 400,000 and 600,000 soldiers of Romanian origin fought on different fronts of Austria-Hungary, which represented a significant percentage of the Romanian ethnics who lived in those times in the Empire.

According to studies made by the army of the Austro-Hungarian Empire, the dedication of the Romanian military to the interest of Austria-Hungary was reduced, only ethnic Italians of the same empire can compete with them for the last place in a ranking according to devotion to the state, per 100 soldiers. Also, in the first 3 years of fighting, out of about 300,000 Austro-Hungarian deserters, 150,000 were ethnic Romanians. Desertion and the transition to the enemy increased significantly in frequency on the Western Front in the last 2 years of the war, significantly affecting Austro-Hungarian military units in their structure and firepower. This has sometimes resulted in failures of entire front sectors.[49] It is worth mentioning that the Romanian ethnics were informed by the Allied aviation by launching leaflets on the Austro-Hungarian positions, on the creation and existence of the Romanian Volunteer Corps in Russia and on the content of the Darnița Declaration.[50]

Although the first Romanian Transylvanian prisoners in Italy were documented as early as June 1915,[51] it was not until 1916 that the percentage of Romanian prisoners of war from Austro-Hungarian troops became significant,[52] and they were mainly concentrated in northern Italy.[51] Along with prisoners of other nationalities of Austria-Hungary, scattered throughout Italy, they contributed to a better understanding of the ethnic situation of the Austro-Hungarian Empire.[49]

Particularly in the province of L'Aquila, where a strong earthquake destroyed the roads and civil structures on January 13 1915, the need for manpower led to the establishment in Avezzano of a camp with 15,000 prisoners. Over time, the component represented by prisoners of Romanian origin has increased significantly, who have developed a good reputation and a good image among the civilian Italian population. The ease with which Italian citizens were able to communicate with the Romanians in relation to Germans and Hungarians, as well as their spirit of sacrifice associated with the demonstration of being good workers, led to the respect of the Italian civilians towards Romanians. This went to the point where Italian civil solidarity and assistance committees were spontaneously created, reserved for Romanian citizens and their families left in the homeland.[52]

Out of a total of 60,000 prisoners of war of Romanian origin, 36,712 soldiers and 525 officers requested to join the Romanian Legion in Italy. Of the officers, one was a colonel, 5 were majors, 32 captains, 97 lieutenants, 294 sublieutenants, and 96 applicants.[49]

The education given to the volunteers enrolled in the new units, emphasized the development of the Romanian national consciousness and the love for their country, which was to be Romania, a country that many knew only through the hostile propaganda of Austria-Hungary. Also, this education aimed to eliminate the distrust in the new Italian ally, as well as the difficulties of communication with other soldiers from the other Romanian historical regions. The only language used in military service was Romanian. Officers of Romanian origin had a complex training program, which included, among other things, the study of the Italian language.[49]

The ranks of the Austro-Hungarian soldiers enlisted in the Romanian Legion were equivalated to those corresponding of the Italian Royal Army.[53] The sedentary part of the Romanian Legion, under the command of Colonel Camillo Ferraioli, was established at Albano Laziale, and the base camp in the Avezzano camp.[54]

Overall command was now under Erich von Falkenhayn (recently replaced as German Chief of Staff), who started his own counterattack on 18 September. The first attack was on the Romanian First Army near the town of Hațeg; the attack halted the Romanian advance. Eight days later, German troops attacked Sibiu, and on 29 September, the outnumbered Romanians began retreating to the Vulcan and Turnu Roșu passes. The latter, however, had been occupied by Bavarian mountain troops in a flanking movement, and the Battle of Turnu Roșu Pass ended with the Romanians retaking the pass at a cost of 3,000 men. On 17 October the Romanian Second Army attacked the Austro-Hungarians at Brașov, but the attack was repulsed and the counterattack forced the Romanians to retreat from there also. The Romanian Fourth Army, in the north of the country, retreated without much pressure from the Austro-Hungarian troops, so that by 25 October the Romanian army was back to its initial positions.[68] The Central Powers succeeded in taking the strategic initiative in Transylvania by concentrating significant military forces rapidly brought in from the other theatres of operations in Europe and exploiting a quick shift of Romanian units to the battlefront in Dobruja.[64]

Romanian troops repelling an Austro-Hungarian attack, October 1916

In October 1916, the Romanian army mounted a wide-scale operation, the main target of which was the defense of the mountain passes in the Southern and Eastern Carpathians against the ever-stronger pressure of the German and Austro-Hungarian forces. Grim fights erupted in the Prahova Valley, where occupation of the locality of Predeal was one of the major aims pursued by the Central Powers. Given their dramatic character, the clashes for the Predeal town and railway station were frequently compared with the heaviest fights on the Western Front. Similar fights took place in the Bran-Câmpulung area, especially at Dragoslavele and Racoș.[64]

Particular heed was paid to the actions carried on for the defense of the Carpathians' alignment, the fights on the Jiu River. There, the Germans had massed large forces to beat their way south of the mountains. Faced with the enemy threat, the troops of the Romanian First Army, under command of General Ion Dragalina, offered strong resistance. The Romanian soldiers were supported everywhere by the civil population; during the Battle of Târgu Jiu, the town was defended by its inhabitants, men, women and children, young and old. There, a conspicuous figure was cut by Ecaterina Teodoroiu, who was to enter the consciousness of all Romanians as the "Heroine of the Jiu". The operation for the defense of the Carpathians holds a prominent place in Romanian military history not only because it was one of the most difficult operations waged by the Romanian army until then, but also because it was one of the most important as regards the complexity of the actions carried on and the highly valuable lessons derived from their evolution.[64]

Romanian prisoners of war passing by an Austro-Hungarian howitzer at the Turnu Roșu Pass

After the Romanian troops were initially able to stop the German advance on the Jiu Valley, the German army regrouped on 29 October 1916. The German High Command created the Army Group Kühne, headquartered in Petroșani, under the command of General Viktor Kühne. This Army Group included the 11th and 301st Bavarian infantry divisions, which had previously fought the Romanians on the Jiu, the 41st Prussian and the 109th infantry divisions which were transferred from the Riga front, as well as the newly formed 58th Cavalry Corps (z.b.V) under the command of General Egon von Schmettow, which included the 6th and 7th cavalry divisions. The German reserves consisted of the 115th infantry division and two brigades of cyclists. The total manpower of the Army Group amounted to 80,000 troops with 30,000 horses. The Romanian forces could not withstand the new German attack which started on 1 November 1916. The Romanians retreated and on 21 November 1916 the German cavalry entered Craiova. The Romanian army continued its retreat towards the Olt River while the cavalry tried to slow the German advance in order to give it time to organize a defensive line along the Olt. Although the Romanian army made attempts to stop the advance of the German forces, such as in the Battle of Robănești, these were largely unsuccessful.[69]

General Stefan Toshev and Hilmi Paşa observing the fighting around Medgidia

Romanian Navy main warships: NMS Elisabeta cruiser, Năluca-class torpedo boats (three), Siretul-class gunboats (four), training ship Mircea, Brătianu-class river monitors (four), Alexandru cel Bun minelayer and armed liners

Back on the coast, Field Marshal Mackensen and Bulgarian General Stefan Toshev launched a new offensive on 19 October, after a month of careful preparations, and achieved a decisive victory in the Second Battle of Cobadin. The Romanians and Russians were forced to withdraw out of Constanța (occupied by the Central Powers on 22 October). After the fall of Cernavodă, the defense of the unoccupied Dobruja was left only to the Russians, who were gradually pushed back towards the marshy Danube Delta. The Russian Army was now both demoralized and nearly out of supplies. Mackensen felt free to secretly pull a large number of troops back to the town of Svishtov in Bulgaria with an eye towards crossing the Danube river.

In mid-November, after several tactical defeats in the Southern Carpathians (Bran-Câmpulung, Prahova Valley, Jiu Valley), Falkenhayn concentrated his best troops (the elite Alpenkorps) in the south for an attack on the Vulcan Pass. The Battle of Vulcan Pass was launched on 10 November. One of the young officers was the future Field Marshal Erwin Rommel. On 11 November, then-Lieutenant Rommel led the Württemberg Mountain Company in the capture of Mount Lescului. The offensive pushed the Romanian defenders back through the mountains and into the plains by 26 November. There was already snow covering the mountains and soon operations would have to halt for the winter. Advances by other parts of Falkenhayn's Ninth Army also pushed through the mountains; the Romanian army was being ground down by the constant battle and their supply situation was becoming critical.

After conquering the main Romanian sea port of Constanța during the Second Battle of Cobadin, the Central Powers set up a naval base which was used by German seaplanes for raids against Sulina, the last Romanian-held sea port. On 7 November, Romanian anti-aircraft defenses at Sulina (including the old protected cruiser NMS Elisabeta) shot down into the sea one of the seaplanes, killing the commander of the German squadron.[70] This reduced the German seaplane force at Constanța by a quarter, which only consisted of four aircraft in November 1916. The shot down seaplane was of the Friedrichshafen FF.33 type, as these were the only German naval bombers on the Romanian front. In total, from 1916 to 1918, German seaplanes serving on the Romanian front were of four types: Friedrichshafen FF.33, Hansa-Brandenburg W.12, Rumpler 6B and Albatros W.4.[71] In November, the German submarine UC-15 was sent on a minelaying mission off Sulina and never returned, being sunk by her own mines.[72][73] This was probably caused by an encounter with the Romanian torpedo boat NMS Smeul, whose captain surprised a German submarine near Sulina in November 1916, the latter reportedly never returning to her base at Varna. This could only be UC-15, whose systems most likely malfunctioned after being forced to submerge in the shallow waters, upon encountering the Romanian torpedo boat.[74] Her Flotilla briefly remained without a minelaying submarine, until UC-23 was commissioned in early December.

Fieldmarshal von Mackensen leading his forces across the Danube.

On 23 November, Mackensen's best troops crossed the Danube at two locations near Svishtov. This attack caught the Romanians by surprise and Mackensen's army was able to advance rapidly towards Bucharest against very weak resistance. Mackensen's attack threatened to cut off half the Romanian army. In response, the Romanian Command prepared a counter-offensive known under the name of the Battle of the Argeș (part of the Battle of Bucharest) and designated the recently promoted General Constantin Prezan to lead it. The plan envisaged the checking of the advance of the German Ninth Army from the north and north-west, as well as the encirclement and annihilation of the German-Bulgarian-Turkish units deployed south-east of Bucharest.[75] It was a bold undertaking, using the entire reserves of the Romanian army, but it needed the cooperation of Russian divisions to contain Mackensen's offensive while the Romanian reserve struck the gap between Mackensen and Falkenhayn. However, the Russian army would not endorse the plan and did not support the attack.

On 1 December, the Romanian army went ahead with the offensive along the Argeș and Neajlov rivers. Initially, the Romanians experienced success, taking a large number of prisoners, however Mackensen was able to shift forces to deal with the sudden assault and Falkenhayn's forces responded with attacks at every point.[76] Faced with the overwhelming superiority of the invading forces, the Romanian army, its ranks thinned from the previous actions, inferior in equipment and lacking Russian support, failed to check the enemy advance. Although it recorded numerous daring actions (among these the Prunaru Charge, in which the 2nd Roșiori Cavalry Regiment was almost wiped out), the Battle of the Argeș ended unfavourably for the Romanian army.[75] Within three days, the attack had been shattered and the Romanians were retreating everywhere. Bucharest was captured on 6 December by Falkenhayn's cavalry. General August von Mackensen was appointed as the "military governor" of the occupied territories of Romania.[77] The Romanian Second Army made a fighting retreat to the Siret river, which had originally been fortified against the Russians and was facing the wrong direction, but nevertheless would end up proving invaluable, protected as it was by the impassable Danube Delta to the southeast and a flank in the Carpathians in the northwest. Fierce fighting took place in the Battle of Râmnicu Sărat between 22 and 26 December, with Mackensen's forces entering the town on 27 December. Around this time, the Russians began sending numerous reinforcements to Moldavia to prevent an invasion of southern Russia. Southern Romania, including Oltenia, Muntenia, Dobruja, and southern Moldavia, was now in the hands of the Central Powers. While retreating, the Romanians burnt stores of grain and destroyed oil wells to prevent them from being used by the Germans.[75]

On 3 December, the Romanian river torpedo boat Căpitan Valter Mărăcineanu was sunk on the Danube by a mine and one sailor was killed.[78][79]

The remaining Russo-Romanian forces in Dobruja abandoned Măcin on 4 January 1917 and Brăila on 5 January 1917. Toward the end of the month, extreme frost gave the Bulgarians an opportunity to enter the Danube Delta. On 23 January, they attempted to cross the marshes at Tulcea, but suffered heavy casualties to Romanian defenders on the northern bank and stopped. The Romanian Land Forces, supported by the Danube Division of the Romanian Navy and by the actions of the Romanian cruiser NMS Elisabeta at the mouths of the Danube, managed to prevent the Central Powers from advancing into the Danube Delta, keeping it under Romanian control until the end of the war.[80][81] Fighting also ceased in the Carpathian passes, also owing to unfavorable weather. Mackensen's troops were able to capture Focșani on 8 January, but an attempt to break the Siret River line on 19 January failed. Thus, the front stabilized and allowed for the Romanian army to be refitted and rebuilt.

Romania entered the war at a time of strong crisis for the Entente, drawing upon itself numerous enemy forces, fighting on a very long battlefront and having to change its initial campaign plan permanently. But in spite of the human, material and military efforts made by the Central Powers throughout this period, they failed to achieve their fundamental political and strategic goal to defeat Romania and knock it out of the war. Despite heavy casualties, some 250,000 men (almost one third of the manpower mobilized in August 1916) compared to 105,000 Central Power casualties (including 60,000 Germans),[82] and losses of combat material, the Romanian army was still a force taken into consideration by allies and enemies alike and capable of offering resistance to further attacks. Part of the population moved to the free territory, together with the Romanian government, royal court and public authorities, which relocated to Iași. Therefore, the Kingdom of Romania continued to exercise the attributes of an independent and sovereign state, allied to the Entente powers.[75]

Romanian-made Negrei Model 1916 heavy mortar

Fahrpanzer 53 mm gun removed from its turret and installed on a Romanian-built gun carriage (thus made an infantry gun)

In 1917, when both belligerent sides were making huge efforts to win the final victory, for Romania it was vitally important for Romanians to expel the occupying forces, since the existence of the Romanian state depended on it. After the Romanian troops had managed to bring the enemy to a halt at Moldavia's Gates, on the Eastern Carpathians, the Siret River and the Danube Delta alignment in cooperation with Russian military forces, Romania embarked on the reconstruction and strengthening of its combat capability during the first half of 1917 through multiple national efforts under highly complex international circumstances. Considerable measures were taken in all economic branches to rebuild the evacuated factories and workshops, increase the production destined for the national defense and the productivity yielded by the exploitation of the few petroleum and coal resources in the free zones. Agriculture received special attention to help meet basic nutritional needs and ensure a minimal living standard to the population in the free part of the country, and also to assist the refugees who had left their houses in front of the enemy invasion, the Romanian army and the Russian troops (who numbered about one million by early 1917).[83]

With a view to achieving the unity of action of internal political forces that was indispensable to safeguarding the nation's interests, a government of national union was set up in Iași on 24 December 1916, led by Ion I. C. Brătianu. The political life in unoccupied territory adopted a fundamental goal to achieve national consensus to find the means to conclude a successful liberation war. Within this framework, debates on some laws envisaging structural transformations (primarily the agrarian reform to re-allocate land to peasants and the introduction of universal suffrage) responded to popular demands of the citizenry and contributed to the morale of the soldiers in the front lines.[83]

The Romanian army's reconstruction involved both re-organization and modernization. While the forces that had taken part in the big Battle of Bucharest (Army Group Prezan) were reshuffled inland, the Romanian Second Army, which had preserved its combat structures and force to a great extent, remained on the front in southern Moldavia, where, alongside Russian forces, it checked the enemy advance. The reorganization was initiated by King Ferdinand and the Romanian government. It was carried on under their leadership and control in the free national territory, in spite of Russian attempts to shift the Romanian army beyond the Dniester, inside Ukraine. The re-organization pursued the reduction of the effectives of the "Operations Army" to parameters that suited the country's resources for waging a long campaign. The infantry divisions were ensured identical structure to make replacements and maneuvers easier on the battlefront and to have a fire power comparable with that of the enemy. The army corps became only a command body for tactical coordination. The cavalry divisions received more machine guns. The artillery material underwent a homogenization process, with two regiments (one cannon, the other howitzer) for each division, while the heavy artillery was organized as a distinct group.[84]

The re-organization also involved the other troops (combat engineers, air force, navy) and services, which underwent notable improvements. The directions, organization and methodology of the training of the command staff and the troops were considerably improved and special training centers were set up. Priority was given to trench warfare, the assimilation of new military technology and night combat.[85]

Considerable progress was achieved with the technical-material equipment of the army by means of its provisioning with armament, ammunition and other combat resources from inside the country, but even more importantly from abroad. The Allies supported the maintenance of the Romanian front by continuing to deliver and supplement previously placed orders.[85] 150,000 French 8 mm rifles, 1,760 Hotchkiss M1914 machine guns, 197 Vickers machine guns, 2,628 Chauchats, 108 Lewis guns, 1.3 million F1 grenades, 84 Puteaux 75mm guns, 72 long and 20 short de Bange 120 mm guns, 28 Coventry 127 mm howitzers, 14 St. Chamond 155 mm and seven Schneider-Putilov 152.4 mm howitzers and 130 French 58mm trench mortars arrived from Western Europe.[86] In parallel, efforts were made to meet the food and health care needs and special heed was paid to strengthening the soldiers' morale. A notable contribution to the reconstruction of the Romanian army was made by the 1,600-strong French military mission led by General Henri Mathias Berthelot, which supervised the process and helped retrain Romanian troops. In early June 1917, the Romanian army's strength grew to about 700,000 men, organized in 207 infantry battalions plus 60 march battalions, 110 cavalry squadrons and 245 artillery batteries, divided among two armies and five corps. The results obtained in terms of re-organization and recovery impressed public opinion both at home and abroad and were to be confirmed in the great battles of the ensuing months.[85]

In January 1917, the Romanian river gunboat Smârdan was sunk by German shore artillery, three sailors were killed.[87] On 16 April, Easter Monday, the Romanian torpedo boat NMS Smeul capsized in rough seas off the mouth of the Danube with the loss of 18 of her crew, including 3 French naval officers present on board.[88] This incident has been incorrectly attributed to Ottoman mines in several English language sources, possibly as a result of wartime propaganda by the Central Powers.[89][90]

Aware of the complex strategic situation, the Romanian Command lent its military policy a clear, realistic orientation of committing the entire population to battle, trying to act efficiently in keeping with the national goals and in harmony with the large-scale operations worked out at the coalition level. Its final form ready in late May 1917, the operations plan for the Romanian front called for the mounting of a general offensive in the Focșani-Nămoloasa sector with a view to completely pin down all enemy forces there, annihilate the main enemy groups operating there (the German Ninth Army) and support the Kerensky Offensive.[91] The decisive effort was to be made by the Romanian First Army. In order to increase the effect of the offensive and draw as many enemy troops as possible northwest of the town of Focșani, the actions of the Romanian Second and Russian Fourth Armies had to precede those of the Romanian First Army. The German High Command, which had moved the center of gravity of its military operations to the Eastern Front in hopes of winning a victory there through the defeat of Romania and the conclusion of a peace with Russia, decided in June 1917 to mount a wide-scope offensive in the north and south of Moldavia, to which end it brought over reinforcements from the other fronts.[92]

In early July 1917, on the Romanian front, one of the largest concentrations of combat forces and war material assembled during World War I: nine armies, 80 infantry divisions with 974 battalions, 19 cavalry divisions with 550 squadrons and 923 artillery batteries, whose effectives amounted to some 800,000 men, with about one million in their immediate reserve. The three great battles, decisive for the Romanian nation's destiny, delivered at Mărăști, Mărășești and Oituz, represented a turning point in the war on the Eastern front. These battles were fought approximately on the front alignment stabilized in early 1917, which the conflicting sides had thoroughly consolidated for half a year.[93]

Romanian Model 1912 105 mm howitzer during the Battle of Mărăști

The Battle of Mărăști began on 24 July 1917 at dawn, and took place in Vrancea County in the sector of the Romanian Second and Russian Fourth Armies. Initiated by surprise with three divisions, the offensive succeeded in disrupting the well-organized enemy defenses and compelling the Austro-Hungarians and Germans to retreat. By the evening, the Romanian divisions had conquered the first defenses, the strongest and deepest of the defensive system of the Gerok Group of the Austro-Hungarian First Army in the Mărăști area. The next day, pursuing the offensive, the Romanian troops forced the enemy into an ever more disorderly retreat. This created favorable conditions for a deep penetration into the defensive disposition and the annihilation of the enemy group. However, under the circumstances in which the Russian High Command decided unilaterally to stall any offensive as a result of the grave situation created on the front in Galicia and Bukovina following the failure of the Kerensky Offensive and the counter-attack of the Central Powers, the Romanian General Headquarters saw itself compelled to discontinue the offensive throughout the entire territory between the Eastern Carpathians and the Black Sea. In the Mărăști zone, however, the Romanian units continued the offensive until 30 July upon the request of their commander, General Alexandru Averescu. This marked the end of the Battle of Mărăști. It inflicted important losses upon the Austro-Hungarians and Germans, who relinquished a 35 km-wide and 20 km-deep area and sustained heavy casualties and losses in combat resources. The offensive potential of the Romanian army was confirmed through this victory.[93]

The salient created by the Romanian troops in the enemy lines at the junction between the Austro-Hungarian First Army and the German Ninth Army made the High Command of the Central Powers bring forces from other sectors on the Moldavian front and change the main direction of the offensive initially planned for the Focșani-Nămoloasa region. After the Mărăști operation had been discontinued, the Central Powers tried to implement their offensive plan in the summer of 1917. They pursued to encircle and smash the Romanian and Russian forces through a blow dealt to the northwest in the direction of Focșani, Mărășești and Adjud, conjugated with another blow that had to start from the mountains through the Oituz and Trotuș valleys towards Târgu Ocna and Adjud (the Third Battle of Oituz). Pursuing the offensive, the German troops aimed at occupying the whole of Moldavia, thereby knocking Romania out of the war, and, together with an in-depth penetration of the Austro-Hungarian troops on the front in Bukovina, to push the Russian forces eastwards, beyond Odessa. The offensive of the German Ninth Army, from the Army Group Mackensen, started on 6 August 1917, when the units of the Russian Fourth Army on the Siret River were expected to leave their positions to reinforce the front in the north of Moldavia and be replaced by the divisions of the Romanian First Army (commanded by General Constantin Cristescu until 12 August, then by General Eremia Grigorescu).[94]

King Ferdinand decorating soldiers at the front

For 29 days, until 3 September, this sector was the scene of the most important battle fought by the Romanian army during the 1917 campaign. The Battle of Mărășești had three distinct stages. During the first stage (6-12 August), the troops of the Romanian First Army, together with Russian forces, managed to arrest the enemy advance and forced the Germans to change the direction of their attack toward the northwest gradually. In the second stage (13-19 August), the Romanian Command completely took over the command of the battle from the Russians. The confrontation reached its climax on 19 August, with the result that enemy's attempts to advance were completely thwarted. The third stage (20 August - 3 September) actually saw the last German attempt at least to improve their positions in view of a new offensive, this one also confounded by the Romanian response.[95]

Starting on 8 August 1917, the fighting on the Mărășești front combined with an Austro-Hungarian-German offensive at Oituz. Holding out against superior enemy forces, the Romanian troops by 30 August stemmed the advance of the Gerok Group. The definitive cessation of the general offensive on the Romanian front by the Central Powers on 3 September 1917 marked a strategic defeat and a considerable weakening of their forces on the South-Eastern front. The response of the Romanian army in fact created the strongest blow to the Central Powers that was dealt in Eastern Europe in 1917.[95]

SMS Inn

As a result of these operations, the remaining Romanian territories remained unoccupied. Nearly 1,000,000 Central Powers troops were tied down, and The Times was prompted to describe the Romanian front as "The only point of light in the East".

On 22 September, Romania achieved its greatest naval success of the war, when the Austro-Hungarian river monitor SMS Inn struck a Romanian mine and sank near Brăila, the explosion killing the chief of staff of the Austro-Hungarian Danube Flotilla and a telegraphist and wounding 8 more sailors.[96][97][98][99]

The situation, however, once again took a turn for the worse for the Entente in November 1917 with the October Revolution in Russia and the beginning of the Russian Civil War. These events effectively ended Russian involvement in the war and left Romania isolated and surrounded by the Central Powers. It had little choice but to negotiate the Focșani Armistice, signed by the combatants on 9 December 1917.

Alexandru Marghiloman signing the Treaty of Bucharest in 1918

The Arcul de Triumf in Bucharest marks Romania's victory in the First World War.

On 7 May 1918, in light of the existing politico-military situation, Romania was forced to conclude the Treaty of Bucharest with the Central Powers. It imposed harsh conditions on the country, but recognized its union with Bessarabia. Alexandru Marghiloman became the new German-sponsored prime minister. King Ferdinand, however, refused to sign the treaty. The Germans were able to repair the oil fields around Ploiești and by the end of the war had pumped a million tons of oil. They also requisitioned two million tons of grain from Romanian farmers. These materials were vital in keeping Germany in the war to the end of 1918.[100]

After the successful Vardar Offensive on the Macedonian front that knocked Bulgaria out of World War I in the autumn of 1918, Romania re-entered the war, again on the side of the Allies, on 10 November 1918. This happened the day before the war ended in Western Europe, a day which marked the start of the Hungarian–Romanian War.

On 28 November 1918, the Romanian representatives of Bukovina voted for union with the Kingdom of Romania, followed by the proclamation of a Union of Transylvania with Romania on 1 December 1918 by the National Assembly of Romanians of Transylvania and Hungary, gathered at Alba Iulia, while the representatives of the Transylvanian Saxons approved the act on 9 January 1919 at an assembly in Mediaș (Medgyes). A similar gathering was held by the minority Hungarians in Cluj (Kolozsvár), on 22 December 1918, where they reaffirmed their allegiance to Hungary.

Germany agreed under the terms of the Treaty of Versailles (Article 259) to renounce the benefits provided by the Treaty of Bucharest in 1918.[101]

The Romanian occupation of Transylvania was widely resented by Hungarians. The Hungarian–Romanian War ended with the Romanian army entering Budapest and the fall of the Hungarian Soviet Republic. The Romanians departed back to the demarcation lines only in early 1920.

• 
  The Carpatho-Danubian region in 1914, before the start of World War I.
• 
  Map of the Treaty of Bucharest (1916), 10 days before Romania's entry to the war. The Entante's promises are highlighted in yellow.
• 
  The extent of Romania's advance into Transylvania before the counteroffensive of the Central Powers.
• 
  Map after the Armistice of Focșani.
• 
  Map after the Treaty of Bucharest, which was never ratified by King Ferdinand I.
• 
  Map of Greater Romania in 1924, after consolidating the borders of the Treaty of Trianon.

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