The Gazala Line ran roughly 50 kilometers from the Mediterranean coast at Gazala, west of Tobruk, south to the old Ottoman fortress at Bir Hakeim. It was not a continuous trench but a series of defensive "boxes," each holding a brigade group behind minefields and wire. The 1st South African Division held the northern sector nearest the coast, the 50th Northumbrian Infantry Division the center, and the 1st Free French Brigade the isolated position at Bir Hakeim in the south. Behind the line, armored divisions waited as a mobile reserve. The minefields were deep and extensive, but the line had a fundamental weakness: its southern end was open desert, and a force willing to drive far enough around Bir Hakeim could get behind the entire position. Rommel knew this. His plan, Operation Venice, called for a decoy attack on the northern Gazala positions while the main armored force -- the Afrika Korps, the XX Motorized Corps, and the 90th Light Division -- swept around the southern flank under cover of darkness.

The flanking move did not go as planned. The Free French garrison at Bir Hakeim, which Rommel had expected to brush aside, fought with extraordinary tenacity, holding out for more than two weeks and leaving the Axis with a dangerously long and exposed supply route around the Gazala Line. Rommel adapted by pulling his armor into a defensive position backed against the Allied minefields -- a position the British dubbed "the Cauldron." Italian engineers then cut gaps through the minefields from the west to create a shorter supply route. When the British launched Operation Aberdeen to destroy the trapped Axis force on 5 June, the attack was poorly coordinated. An artillery bombardment meant to suppress Axis anti-tank guns fell in the wrong location due to a plotting error, and advancing British tanks ran into massed anti-tank fire that had not been touched. The 32nd Army Tank Brigade lost fifty of its seventy tanks. Rommel split his forces and counterattacked, overrunning the headquarters of two British divisions and scattering several Indian infantry brigades left stranded without armored support.

By 13 June -- a date the Eighth Army came to call Black Saturday -- the cumulative losses were catastrophic. British tank strength had fallen from over 300 to roughly seventy operational vehicles. The Afrika Korps, combining tanks with anti-tank guns and acting rapidly on intelligence from Allied radio intercepts, had established armored superiority across the battlefield. The Knightsbridge defensive box, its commanding officer killed the previous day, was virtually surrounded and abandoned by the Guards Brigade during the night. With the armored balance broken, the infantry divisions on the Gazala Line faced being cut off entirely. Ritchie ordered the Eighth Army to withdraw. The 1st South African Division retreated along the coast road largely intact, but the 50th Northumbrian Division, unable to move east because of Axis tanks, had to attack southwest through the Italian lines, then loop south into the desert before turning east -- a desperate maneuver that succeeded only because the Italian divisions they broke through lacked the strength to stop them.

Tobruk had withstood an eight-month siege in 1941. In June 1942, it fell in twenty-four hours. The fortress's defenses had not been maintained, its garrison consisted largely of inexperienced troops, and a series of ambiguous communications between Auchinleck and Ritchie left it besieged rather than evacuated as originally planned. On 20 June, the Panzerarmee penetrated a weak spot on the eastern perimeter and drove into the port. Some 33,000 men surrendered, many on the western perimeter having never been engaged. The Axis captured over 1,000 working vehicles, vast stocks of food, and large quantities of fuel. Hitler rewarded Rommel with a promotion to field marshal -- the youngest German officer ever to hold the rank. Rommel remarked that he would have preferred another panzer division. Churchill, receiving the news while visiting Roosevelt in Washington, called it a disgrace: the largest capitulation of British Empire forces since Singapore four months earlier.

The Eighth Army suffered approximately 50,000 casualties, including the garrison at Tobruk. German losses were about 15 percent of their force; Italian casualties included 3,000 men, 125 tanks, and 39 guns. Rommel pursued the retreating British into Egypt, forcing them out of a defensive position at Mersa Matruh and driving them back to El Alamein, where Auchinleck -- having dismissed Ritchie and taken personal command -- finally stopped the advance at the First Battle of El Alamein in July. But Gazala's consequences extended beyond the battlefield. To support Rommel's dash into Egypt, the planned Axis invasion of Malta was postponed indefinitely. This allowed the British to revive Malta as a base for attacking Axis supply convoys, creating the logistical stranglehold that would cripple Rommel at El Alamein. The greatest victory of Rommel's career contained the seed of his eventual defeat.