Despite Metaxas’ strategy of armed neutrality and his wish to stay out of the war unfolding, Greece was forcedly involved in World War II on 28 October 1940, when the Italian Army invaded from Albania, beginning the Greco-Italian War. The Greek Army was able to halt the invasion and was able to push the Italians back into Albania, but it was precisely these Greek successes the ones which forced Nazi Germany to intervene to help its parner Mussolini.

The Germans launched a long-anticipated attack on 6 April 1941, not only on Greece but also on Yugoslavia at the same time. The initial attack (Unternehmen Marita) came against the Greek positions of the “Metaxas Line” (19 forts in Eastern Macedonia between Mt. Beles and River Nestos and 2 more in Western Thrace). It was launched from Bulgarian territory and supported by artillery and bomber aircraft.

The resistance of the forts under general Konstantinos Bakopoulos was both courageous and determined, but eventually futile. The rapid collapse of Yugoslavia had allowed the 2nd Panzer Division (which had started from the Strumica Valley in Bulgaria, advanced through Yugoslav territory and turned south along the Vardar/Axios River valley) to bypass the defenses and the Germans captured the vital port city of Thessaloniki on April 9.

As a result, the Greek forces manning the forts (the Army Section of Eastern Macedonia, TSAM) were cut off and given permission to surrender by the Greek High Command. The surrender was completed the next day, April 10, the same day that German forces crossed the Yugoslav-Greek border near Florina in Western Macedonia, after having defeated any resistance in southern Yugoslavia. The Germans broke through the Commonwealth (2 div. & 1 arm. brig.) and Greek (2 div.) defensive positions in the Kleidi area on April 11/12, and moved on to the south and southwest.

While pursuing the British southwards, the southwest movement threatened the rear of the bulk of the Greek Army (14 divisions), which was facing the Italians at the Albanian front. The Army belatedly began retreating southwards, first its northeast flank on April 12, and finally the southwest flank on April 17. The German thrust towards the northern Greek city of Kastoria on April 15 however made the situation critical, threatening to cut the Greek forces’ retreat. The generals at the front began exploring the possibilities for capitulation (to the Germans only, not to the Italians), despite the High Command’s insistence in Athens on continuing the fight to cover the British retreat.

In the event, several generals under the leadership of Lt. Gen. Georgios Tsolakoglou mutinied on April 20, and taking matters in their own hands, signed a protocol of surrender with the commander of the “Leibstandarte SS Adolf Hitler” near Metsovo the same day. It was followed by a second in Ioannina the next day (with Italian representation this time) and a final one in Thessaloniki between the three combatants on the 23rd. The very same day in Athens, Lt. General A. Papagos resigned his office as Supreme Commander whereas the King and a fraction of the government embarked for Crete – marking the end of the 4th of August regime.

About the same time the Commonwealth forces made a last stand at Thermopylae before their final retreat to the ports of Peloponnese for evacuation to Crete or Egypt. German troops seized the Corinth Canal bridges, entered Athens on April 27, and completed their occupation of the mainland and most islands by the end of the month, along with the Italians and Bulgarians.

The only Greek territory remaining free by May 1941 was the large and strategically important island of Crete, which was held by the remaining Greek troops and a large but weak Allied garrison consisting primarily of the combat-damaged units evacuated from the mainland without their heavy equipment, especially transport. To conquer it, the German High Command prepared “Unternehmen Merkur”, the largest airborne attack seen to date.

The attack was launched on May 20, 1941. The Germans attacked the three main airfields of the island with paratroopers and gliders. The Germans met stubborn resistance from the military on the island as well as from local civilians. At the end of the first day, none of the objectives had been reached and the Germans had suffered around 4,000 casualties.

After seven days of fighting the Allied commanders realized that so many Germans had been flown in that hope of Allied victory was gone. By June 1, the evacuation of Crete by the Allies was complete and the island was under German occupation. With the capture of Crete, the conquest of Greece was completed and the Greek-German war was considered ended in May.