31 March incident

The murder of Hasan Fehmi, editor-in-chief of the anti-CUP newspaper Serbestî, in the days preceding the mutiny acted as a catalyst for unrest.

In October 1908, the Committee of Union and Progress arranged for the transfer of three seasoned sharpshooter (Avci) battalions of the Third Army Corps from Salonika to Istanbul in response to increased political tension in the city and concerns over the loyalty of its regular garrison, the First Army Corps.[18] The Third Army's mektepli officers – graduates of the prestigious Ottoman Military College trained in modern military techniques – had played an instrumental role in the 1908 revolution.[15] Upon their arrival in Istanbul, the well-connected mektepli officers began to play an important role within the capital's political and social scene, attending CUP political functions, banquets and theatrical performances. With their officers increasingly absent, discipline within the sharpshooter battalions began to break down.[18] A generational divide exacerbated the poor relationship between the officers and their men, as opponents of the CUP within the military expressed unhappiness with entrusting the empire's leadership to "yesterday's school children", the young CUP officers recently graduated from military academies, at the expense of more experienced officers who had climbed the ranks. The situation worsened when the newly elected parliament announced its intention to retire a significant part of the officer corps, with cuts disproportionately affecting non-commissioned officers.[19]

In late October, authorities arranged for the transfer of Albanian troops seen as hostile to the new regime out of Istanbul. Many of these soldiers were soon due to be discharged, and upon receiving orders for deployment to Yemen a portion refused and demonstrated for the immediate termination of their contracts.[13] Troops from the fourth Avci battalion were sent to suppress the protests by force and a second riot among Albanian troops in March was again put down by Avci troops, who fired into the riotous crowd of Albanians with machine guns. These events severely damaged morale among the sharpshooters.[20] In February 1909, Grand Vizier Kâmil Pasha moved to weaken the CUP's grip on power by appointing his own candidates as Ministers of War and Navy. In response, the CUP orchestrated a confidence vote against his cabinet, forcing him to resign.[20] On 14 February 1909, the CUP's preferred candidate, Hüseyin Hilmi Pasha, was appointed the new grand vizier.[21] Rumours spread within the city that the CUP would use the Avci troops to depose Abdul Hamid, or that Kâmil Pasha had attempted to order them back to Macedonia.[20] As a consequence of these machinations, the battalions became increasingly politicised and, to the frustration of ordinary soldiers, seen as a tool of the CUP.[20]

Discontent among the soldiers was further stirred up by Muslim fundamentalists. Islamists in Istanbul were led by a charismatic mystic from Cyprus called Hafiz Derviş Vahdeti, who may have belonged to the Bektashi Order.[22] Vahdeti established the Society for Islamic Unity, also known as the Mohammedan Union Party, and set up a newspaper called Volkan (Volcano in English) in November 1908 to spread anti-secularist rhetoric and campaign against the government.[23][24] Religious conservatives portrayed the restored 1876 constitution as sacrificing Islamic traditions in order to curry favour with Western states and attacked the new general assembly for giving minorities and Christians within the empire greater influence, issues which resonated with soldiers who had recently been fighting separatists in the Balkans.[25][26] Attempts by the CUP to introduce new mektepli officers and training regimen into the First Army Corps resulted in less time for soldiers to undertake ablution and prayer, allowing Islamists to present the CUP and its officers as irreligious, even atheistic, free masons from Macedonia.[27][4] Although Abdul Hamid refused to provide financial support for the movement and newspaper, figures connected with the palace purportedly supported Vahdeti and one of the sultan's sons, Şehzade Mehmed Burhaneddin, was a member of the Mohammedan Union.[22] The society held its first mass rally on 3 April at the Hagia Sophia; its agitation for the restoration of Sharia gained widespread support, including from soldiers stationed in the city.[22]

On 6 April, Hasan Fehmi, a prominent opposition journalist, was shot and killed as he crossed Galata Bridge in Istanbul. The assassination went unsolved but many in the city speculated that the CUP had been responsible.[28] Protests by Islamic conservatives and seminary students over the killings led to unrest among soldiers in the city's main barracks.[28]

Tashkishla barracks at Taksim following the suppression of the uprising

Early on the morning of 13 April, troops of the fourth Avci regiment based at the Tashkishla barracks mutinied, locking up their officers and marching onto the streets to call for the reinstatement of Sharia and for the CUP to be disbanded.[15] Religious students joined the mutinying soldiers outside the Sultan Ahmed Mosque, before marching to the parliamentary building.[22] Hilmi Pasha's government was in a state of confusion, and fearful of the repercussions of ordering remaining loyal troops against the protestors, it sent the Chief of Police instead to hear the crowd's requests.[29] Six demands were prepared by the spokesmen of the mutineering soldiers: the return of Sharia law, the banishment of some CUP parliamentarians from Constantinople, the replacement of Ahmed Rıza (the CUP President of the Chamber of Deputies), the replacement of some CUP officers and the removal of the Grand Vizier along with the Ministers of War and Navy.[29] By the afternoon the government's authority in the capital had collapsed, and faced with this ultimatum Hilmi Pasha and his cabinet resigned. The Sultan swiftly appointed Ahmet Tevfik Pasha as grand vizier.

Marshal Ethem Pasha, the War Minister of the new cabinet went to see the troops at Meydanı, gave them praise and told them that their requests would be fulfilled.[30] The victory was celebrated by the soldiers and religious students.[30] During the revolt, the CUP was targeted in a pogrom with protestors killing 20 people, mainly army officers, and two parliamentarians mistaken for Ahmet Rıza and Hüseyin Cahit (Yalçin), the editor of the CUP newspaper Tanin.[31][30] Protestors also burned a few CUP offices such as those belonging to Tanin.[31][30]

From 15 April the CUP began preparations for a military operation against the rebels.[36] It appealed to Mahmud Shevket Pasha, commander of the Ottoman Third Army based in Selanik (modern Thessaloniki) to quell the uprising.[31] With support from the commander of the Ottoman Second Army in Edirne, Mahmud Shevket combined the armies to create a strike force called the "Action Army" (Hareket Ordusu).[31] The force numbered 20,000–25,000 regular troops,[31] reinforced with volunteer units, mostly Albanians led by Major Ahmed Niyazi Bey.[36] The eleventh Reserve (Redif) Division based in Selanik composed the advance guard of the Action Army and the chief of staff was Mustafa Kemal Pasha.[37][38]

Action Army forces marching on Bakırköy

In short time CUP members Fethi Okyar, Hafız Hakkı and Enver Bey returned from their international posts at Ottoman embassies and joined Mahmud Shevket and his military staff prior to reaching Istanbul.[39][37] The Action Army's troops were transported by train to Çatalca and Hademköy, and then to Ayastefanos (also referred to as San Stefano; modern Yeşilköy).[36] It was secretly agreed there that Abdulhamid would be deposed for his brother Reşad. A delegation was sent to Army headquarters by the Ottoman Parliament that sought to stop it from taking Istanbul through force.[37][37] The response was negative and the delegation then went to Ayastefanos and made a call for colleagues to unite with them.[37] Both parliamentary chambers convened as a National Assembly (meclis-i umumi-i milli) at the Yachting Club building of Ayastefanos on 23 April and thereafter.[37] Qemali had left the city prior to the Action Army arriving at Constantinople and he fled to Greece.[40]

The Sultan remained in the Yildiz and had frequent conferences with Grand Vizier Tewfik Pasha who announced:

His Sublime Majesty awaits benevolently the arrival of the so called constitutional army. He has nothing to gain or fear since his Sublimity is for the Constitution and is its supreme guardian.[41]

Negotiations continued for six days. The negotiators were Rear Admiral Arif Hikmet Pasha, Emanuel Karasu Efendi (Carasso), Esad Pasha Toptani, Aram Efendi and Colonel Galip Bey (Pasiner). Finally, at the moment when the conflict showed signs of extending to the public, the Salonikan troops entered Istanbul.

Action Army forces entering Istanbul

Early on the morning of 24 April the Action Army began to occupy Istanbul,[42] with the operation directed by Ali Pasha Kolonja.[43] There was little meaningful resistance, with the exception of Tașkışla and Taksim barracks; by four o'clock of the afternoon the remaining rebels surrendered.[42]

The execution of the countercoup rebels in the journal Resimli Kitap, 1909

There was fierce street fighting in the European quarter where the guard houses were held by the First Army Corps. There was heavy fire from troops in the Tashkishla barracks against the advancing troops. The barracks had to be shelled and almost destroyed by the artillery located on the heights above the barracks before the garrison surrendered after several hours fighting and heavy losses. Equally desperate was the defence of the Taksim barracks. The attack on the Taksim barracks was led by Enver Bey. After a short battle they gained control of the palace on 27 April.[44]

Under martial law and following the defeat of the rebellion two courts martial sentenced and executed the majority of the rebels which included Dervish Vahdeti.[42] Albanians involved in the counterrevolutionary movement were executed such as Halil Bey from Krajë which caused indignation among conservative Muslims of Shkodër.[43] Some Liberal (Ahrar) political leaders were arrested and British pressure resulted in their freedom.[42] A government investigation later cleared Qemali of any wrongdoing.[34] Sultan Abdul Hamid was deserted by most of his advisors. The parliament discussed the question as to whether he would be permitted to remain on the throne or be deposed or even be executed. Putting the Sultan to death was considered unwise as such a step might rouse a fanatical response and plunge the Empire into civil war. On the other hand, there were those who felt that after all that had happened it was impossible that the parliament could ever again work with the Sultan.[45]

On 27 April the Assembly held a meeting behind closed doors under the presidency of Said Pasha. In order to remove the Sultan, a fatwa was needed.[46] So, a fatwa drawn up in the form of question and was given to scholars to answer and sign. A scholar by the name of Nuri Efendi was brought to sign the fatwa. Initially, Nuri Efendi was unsure whether three crimes raised in the question were carried out by Abdulhamid. He initially suggested that it would better to ask the Sultan to resign. It was insisted that Nuri Efendi sign the fatwa. However Nuri Efendi continued to refuse. Finally, Mustafa Asim Efendi convinced him and so the fatwa was signed by him and then it was signed by the newly appointed Sheikh ul Islam, Mehmed Ziyâeddin Efendi, legalising it.[46][47] The fatwa complete with the answer was now read to the assembled members:

If an imam of the Muslims tampers with and burns the sacred books.
If he appropriates public money.
If after killing imprisoning and exiling his subjects unjustly, he swears to amend his ways and then perjures himself.
If he causes civil war and bloodshed among his own people.
If it is shown that his country will gain peace by his removal and if it be considered by those who have power that this imam should abdicate or be deposed.
Is it lawful that one of these alternatives be adopted.
The answer is "Olur" (it is permissible).[48]

Then the Assembly unanimously voted that Sultan Abdul Hamid should be deposed.