 On 6 April the German invasion of Greece and Yugoslavia began. In order to help defend Greece, a composite force of three divisions of Australian, British and New Zealand troops were to be deployed, and were grouped together under the title of 'W' Force. However, by the time the invasion began only two of the three divisions had arrived, and the New Zealanders were consequently spread thin, holding a position to the north of Katerini, where they were tasked to defend the strategic Olympus Pass to the south. During this time, the 28th (Māori) Battalion was attached to the 5th Infantry Brigade, which was later grouped with other Australian and New Zealand units to form the Anzac Corps. Vastly outnumbered, within two days the situation for the Allies was not good as the Germans had broken through the defences along the Bulgarian border and the Yugoslav resistance had collapsed. As the situation worsened, orders came down from brigade headquarters that the passes would be held "to the last man and last round".
