On the 17th April Yugoslavia capitulated to the German Army. The whole force of the German Armies now fell on Greece. On 20th April the Greek armies on the Albanian front surrendered. With their left flank exposed, the British had to retreat from their position at Thermopylae. On 24th April the Greek government surrendered and the British evacuation of Greece began. The British still held the island of Crete with its important harbour of Suda Bay; but Hitter was determined to secure this essential forward base for the protection of the Balkans and for attack on Egypt (Directive 28). After that, he would be prepared to leave the task of occupying Greece largely to the Italians, who were still unaware of his plans for a far greater campaign in the east (Directive 29).