To some extent, the impression that the Greeks had collapsed was a false impression. The Greeks were poorly equipped and were in poor uniforms and were walking along the side of roads. One feature was that it was services troops that were in retreat, while the fighting men were still in place, holding out. General Wilson was concerned about "his inland flank". One concern was that the Germans might move rapidly along the Grevena road to the "Larisa bottleneck". That would cut the road to Athens for the British forces. Wilson decided to use the Australian 17th Brigade, only just arriving at the Piraeus, as his flank protection. 

It was only on 13 April that the 17th Brigade commander arrived at General Blamey's headquarters. The 17th Brigade had "reached Larisa on 11 April". On 12 April, they were still in Athens. It turns out that General Wilson was at Blamey's headquarters when the 17th Brigade commander, Brigadier Savige had arrived. 

General Mackay gave orders to the 19th Australian Brigade. They were to thin out the infantry and get on vehicles in preparation to withdraw. He wanted them to be on vehicles by "4am on 13 April. A rearguard position was to be held at Rodona and Sotir. This would be some six miles to the south. They would need to "cover the main withdrawal". The German attack that they had expected started at 8:30am on 12 April. The Australians were surprised that the Germans did not disperse to defend against air attack, which the Australians always did. This is based on the account in "Greece Crete and Syria" by Gavin Long.