The following month, the 9th Division was sent forward into the Western Desert to relieve the 6th Division following their victories at Bardia and Tobruk. The 6th Division was to be sent to Greece where a German invasion was expected, and so the 20th Brigade and took over from the 17th around Marsa Brega in Cyrenaica. A further move was undertaken to Er Regima, where the brigade was tasked with holding approaches around the Benghazi Plain. After German forces landed around Tripoli to reinforce the Italians in North Africa, a large scale withdrawal began as the British and Australian forces were pushed back towards Tobruk, which was subsequently surrounded and placed under siege. During the withdrawal, the 2/15th Battalion's headquarters was surrounded and captured after attempting to fend off an attack by German tanks, while the 2/13th fought a more successful delaying action around Er Regina. Between April and October 1941, the 20th Brigade took part in the defence of the strategic port, helping to hold back the German thrust around the El Adem Road and then holding the line at various points around the perimeter. Finally, they were relieved by the British 14th Infantry Brigade and withdrawn by sea.