The British plan for Operation Brevity included three columns. The 2/Rifle Brigade would take the bottom of Halfaya Pass and then move on to Salum (or Sollum). The 22nd Guards Brigade with the 4th/RTR would capture the top of Halfaya Pass and then move northwards. They would have 24 infantry tanks. The open desert flank would be taken by the 7th Armoured Brigade. They had the 2/RTR with 29 cruiser tanks. They also had three Support Group columns in support. The support group columns each had an Australian anti-tank gun troop. The 12th Anti-Tank Gun Battery commander was with one of the columns. The headquarters was sitting on the coast. They had a troop from 5th Battery, 2/2nd Anti-Tank Regiment, another Australian unit. All the action started at dawn on 15 May 1941.
Even though the Germans had expected the attack, the British still achieved surprise. The Guards Brigade and the infantry tanks were able to quickly capture "the top of Halfaya Pass". The bottom of Halfaya Pass did not give up so easily. They bottom fell only by 5pm. The center group also captured Salum with 123 prisoners. Fort Capuzzo was also taken, but most of the attacking infantry tanks were disabled.
The attack achieved enough success to cause the German command some anxiety. Partly, this was because reports enlarged the attacking force beyond what was actually used. Motorized and mechanized units near Tobruk were redeployed to be ready for an attack by British forces from the Egyptian Frontier. One German tank battalion was sent to El Duda. Some Italian tanks were sent to El Adem. A counter-attack by the Herff Group retook Fort Capuzzo displaced the Durham Light Infantry and took some prisoners. The British did not have a good tank recovery system in place, so the disabled infantry tanks were left where they had been abandoned. The British were able to recover a few, destroy others, while the rest ended up in German hands.
Herff reported to Rommel that the British seemed to have some 40 to 50 tanks. Herff expected them to push on towards Tobruk by morning. He would sit on the flank position, ready launch an attack when he was reinforced. The British were actually quite cautious, and Brigadier Gott would move to Halfaya, if the Germans attacked with tanks. Rommel ordered reinforcements to be sent to Herff. Another group of all arms was also ordered to join Herff. The British were much less prepared and General Beresford-Peirse was slow to respond to Gott's message. His initial thought was to order Gott to hold the positions that he had taken. On 16 May, the British tanks withdrew, while the Germans were immobilized due to lack of fuel. This is based on the account in Vol.III of the Australian Official History.