From 24 April till 1 May 1941, over 50,000 troops of the British Expeditionary Forces were evacuated from Greece. Next to a large number of warships, nine troop-ships were involved in this exercise, including three of them of Dutch origin. All three Dutch vessels were sunk whilst the destruction of ss Slamat became the largest disaster at sea in Dutch history.
End 1940 the Italian dictator Benito Mussolini made an effort to step out of the shade of his ally Adolf Hitler by invading Greece. With this, in his eyes easy target, Mussolini wanted to show off with his conquest to what he and Italy were militarily capable of. On the 28th of October, 1940, Italian troops invaded Greece from the earlier conquered Albania. The Greeks however appeared to be tough opposition and the Italians did not succeed in breaking through their defense lines. Within three weeks the Greeks had been able to stop the Italian advance and started the counter attack, which pushed the Italians back across the Albanian border. The Italians called in reinforcements, but on 9 March, 1941, a large counter attack at the Greeks again came to nothing. After a week Mussolini called his troops back and the Greek-Italian War was finished.
In the meantime the German strategy, had already since the beginning of the war, been aimed at removing the Brits from the Mediterranean area. The conquest of Yugoslavia and Greece therefore fitted the German strategic thinking. Herewith the Axis-Powers would make the connection with the German troops in North Africa, who were advancing in the direction of Egypt and Palestine, both being British protectorates. Especially for this reason but also in order to relieve allied Italy, Hitler had decided in November 1940 to invade Greece. From that time German troops regularly had made sorties from Bulgaria and Rumania towards cities in North-Greece. On April the 6th, 1941, the Germans, together with their allies Italy and Bulgaria, launched a massive attack on Yugoslavia and Greece. Ten days later Yugoslavia already had to give in to the German Blitzkrieg and the Balkan country capitulated. On 23 April the Greeks were obliged to do the same.
On request from Greece, but also because of their own interest, the British sent a 60,000 strong Imperial Expeditionary Force to Greece under the code name Operation Lustre. The operation started on the 2nd of March 1941 when the first British, Australian, New Zealander, Palestinian and Cypriote troops boarded in Alexandria, Egypt. On March 26th the first British imperial troops disembarked in Piraeus, the harbor of Athens, and moved to the north. From April the 6th onwards however it appeared quite quickly that the combined Greek and British armies were no match for the Germans. This not only was the result of the 360,000 strong allied armies being numerically in a vast minority compared to the 680,000 German and 565,000 Italian forces, but mainly because the Luftwaffe was lord and master in that region. On 21 April the British government agreed to the proposition of the commander of the British Expeditionary Force, Lieutenant-General Sir Henry Maitland Wilson, to evacuate the troops from Greece. This operation was code named Demon.
Already during the first night of the German offensive, from 6 to 7 April, the Luftwaffe had carried out heavy aerial attacks on Piraeus. That is how the British ammunition carrier Clan Fraser had exploded, but as a consequence of the extreme explosion, not less than 13 other ships had also been sunk. Even worse however was the total destruction of the seaport facilities of Athensís harbor city. This prevented Operation Demon from being carried out from this important port and the British became dependent on smaller harbors like Rafina and Porto Raffi east of Piraeus, Megra west of Athens and Nauplia (Nafplion), Monemvasia and Kalamata on the Peloponnesus peninsula. Because the Luftwaffe did not meet any resistance of significance the allies had to start from the presumption that the German aircraft would have a free play at bombarding the evacuation convoys. Therefor the darkness was their only ally during Operation Demon.