The German invasion of Greece on 6 April 1941, had already been anticipated by the Allied forces. So a defense line was created across the mountain passes near Mount Olympus consisting of British, Australian and New Zealand troops which would prevend the German forces from capturing Thessaly and thereby denying them the opportunity to advance into mainland Greece. However, the speed of the German invasion force had made sure that the endurance of the defending troops and the strength of their defences were very quickly going to be put to the test.