Generals Blamey, Mackay, and Freyberg had all fought in the Gallipoli campaign in 1915. Early on 12 April 1941, remembering those days in 1915 when the Australians and New Zealanders had fought together, he declared that from henceforth, the 1st Australian Corps would be known as the ANZAC Corps. This was to celebrate the reunion betweem the Australians and New Zealanders.
At this time, the German plan was to turn the British flank and catch them in the rear with armoured divisions. They had intelligence from Egypt that there were four divisions opposing them. They included the 6th and 7th Australian Divisions and the New Zealand Division, with part of the 2nd Armoured Division. This was certainly the plan, but did not accurately reflect the troops on the ground. The Germans had roared through Yugoslavia, almost unopposed, and then swept towards the British troops. They arrived on 12 April. This is based on the account in Vol.II of the Australian Official History.