Lieutenant Colonel Robert Ogle took over command of the battalion following Marlan's capture. It subsequently joined the defence of Tobruk, as part of the defensive garrison that held the strategically important port after it was placed under siege by the advancing German and Italian forces. The battalion remained there for over six months conducting patrols and raids, and holding positions around the perimeter until late October 1941, when the bulk of the 9th Division, less the 2/13th Battalion and two companies from the 2/15th, were withdrawn by sea and replaced by British troops from the 70th Division. The 2/15th's casualties during the withdrawal from Benghazi and the siege of Torbuk amounted to 45 killed in action or died of wounds, one accidentally killed, 103 wounded in action and 205 captured.