Balkans campaign (World War II)

The Italian invasion of Greece lasted from 28 October 1940 to 30 April 1941. Italian forces invaded Greece and made limited gains. But soon the Greeks counter-attacked and the Italians were driven back to the Albanian border. The Italians spent much of the winter stabilizing a line which left them in control of only about two-thirds of Albania. A much anticipated Italian offensive in March 1941 resulted in few territorial gains. Germany, led by Adolf Hitler, intervened in April and invaded Greece after the successful invasion of Yugoslavia.

The invasion of Yugoslavia (also known as "Operation 25") began on 6 April 1941 and ended with the unconditional surrender of the Royal Yugoslav Army on 17 April. The invading Axis powers (Nazi Germany, Fascist Italy, and Hungary) occupied and dismembered the Kingdom of Yugoslavia. By cobbling together Bosnia and Herzegovina, some parts of Croatia, and Syrmia, the "Independent State of Croatia" (Nezavisna Država Hrvatska, NDH) was created by Germany and Italy. In some of the territory of the former Kingdom of Serbia and the Banat, the German-occupied Territory of the Military Commander in Serbia, the Germans appointed a puppet government, the Government of National Salvation led by Milan Nedić. Montenegro remained under Italian occupation, and Bulgaria was permitted to annex eastern areas of Yugoslavia, including most of modern-day North Macedonia.

Hitler began planning to invade Greece in November 1940, after the British occupied Crete and Lemnos. He ordered the invasion of Greece — code-named Unternehmen Marita (Operation Marita) — on 13 December 1940 for execution in March 1941. The stated aim of the operation was to prevent the British from getting air bases within striking range of the Romanian oilfields.[1] On 6 April 1941, the German Army invaded northern Greece, while other elements launched an attack against Yugoslavia. Breaking through the Yugoslav lines in southern Yugoslavia allowed Germany to send reinforcements to the battlefields of northern Greece. The German army out-flanked the Greek Metaxas Line fortifications and, despite the assistance provided by a British expeditionary corps, set out to capture the southern Greek cities. The Battle of Greece ended with the German entry into Athens and the capture of the Peloponnese, although about 40,000 Allied soldiers were evacuated to Crete, prompting one of the largest airborne attacks in the history of warfare: Operation Merkur, or the Battle of Crete.

On 20 May 1941, German paratroopers were dropped over the airfields of northern Crete to occupy the island. They were met by heavy resistance from Allied forces and the local Cretan population but eventually the defenders were overwhelmed by the German forces. The British Government ordered an evacuation on 27 May and the remaining forces surrendered on 1 June. However, the heavy losses incurred by the paratroopers convinced the Supreme Command of the Wehrmacht to abandon large-scale airborne operations for the remainder of the war.

On 6 April 1941, despite having officially joined the Axis Powers, the Bulgarian government did not participate in the invasion of Yugoslavia and the Battle of Greece. On 20 April, the Bulgarian Army occupied most of Western Thrace and the Greek province of Eastern Macedonia, which had been already conquered by Germany, with the goal of restoring its pre-World War I outlet to the Aegean Sea. Bulgarian troops also occupied much of eastern Serbia, where Vardar Banovina was divided between Bulgaria and the Italians.

Throughout the remainder of the war, active Yugoslav, Greek, and Albanian resistance movements forced Germany and its allies to garrison hundreds of thousands of soldiers permanently in the three countries, denying them to the other fronts. Especially in Yugoslavia after 1943, the threat of an Allied invasion and the activities of the partisans necessitated large-scale counter-insurgency operations, involving several divisions.