The defense of Tobruk since May 1941 had been commanded by General Leslie Moreshead, the commander of the 9th Australian Division. The Australians mounted an active defense, mounting constant small operations against the attackers. The Axis surrounded Tobruk with a system of minefields and artillery. Axis aircraft constantly were in the air over Tobruk, harrassing the defenders. A great deal of AA ammunition was expended by the defenders. The attackers did not want to attack until they were able to build up an arsenal of heavy artillery. In the event, the Tobruk garrison not only withstood the attacks but were able to break out during the Crusader battle.
The Australian commander, General Blamey, asked that Australian troops be replaced and withdrawn. That seems to have reflected the desires of the Australian government. The Australian government undoubtedly wanted their troops removed from what seemed to be a vulnerable position, in the besieged port. By August, the first withdrawals took place. By the end of August, there had been a change of government in Australia, and the new Prime Minister pushed for the rest to be removed from Tobruk. That seriously interfered with plans for Crusader and put naval assets under increased risk of attack. General Auchinleck was greatly distressed by the matter and Churchill assured him of their complete confidence in him. This is based on the account in Vol.III of the Official History.