Although Rommel had ended his advance, he took care to fortify positions on the frontier, including Halfaya Pass, Sollum, and Fort Capuzzo. Wavell wanted these as a springboard for his intended relief of Tobruk. He tried to take them in May (Operation Brevity) and again in June (Operation Battleaxe), without success, although the British did have local if temporary successes. But they lost a total of 91 tanks during Battleaxe, including a high proportion from mechanical failure. They claimed to have disabled 100 enemy tanks, which was probably close to the truth, but as the Germans were left in possession of the battlefield they were able to recover all but 12 burned-out hulks. These failures infuriated Prime Minister Winston Churchill, who wanted to appoint a new Commander-in-Chief Middle East. However, Wavell had too many successes to his credit to sack him out of hand. Instead, Churchill promoted him sideways, ordering him to change places with General Sir Claude Auchinleck, Commander-in-Chief India. The German 88mm anti-aircraft gun became notorious when used as an anti tank gun. This weapon when placed in well prepared positions was a very difficult taget to hit.