The siege started on 10 April 1941. It was relieved at the end of November.
Australian troops of the Australian 9th Division and the 18th Brigade of the Australian 7th Division under Lieutenant General Leslie Morshead made up more than half of the Allied presence in Tobruk. There were more than 14,000 men. The rest of the garrison was made up of 12,000 British (the 3rd Armoured Brigade, 4 artillery regiments) and Indian (the 18th King Edward's Own Cavalry) troops.
During the three moonless periods between August and October, the Australian troops and Indian cavalry left by sea and were replaced by British 70th Infantry Division and the Polish Independent Carpathian Brigade with the Czechoslovak 11th Infantry Battalion under command.