During the night of 19-20 June 1942 Rommel discontinued his feigned pursuit of the retreating British and masterfully turned around his four best divisions, the veterans of the old Deutches Afrika Korps: the 90th Light, 15th and 21st Panzer, and the Italian armored division Ariete. That night they moved from an all-out pursuit and prepared to assault Tobruk. At 5:30 am 20 June, every Luftwaffe bomber in the Eastern Mediterranean struck the south east corner of Tobruk perimeter and the defending unit, the 11th Indian Brigade, broke under the combined arms assault by Italian infantry and artillery with German tanks and planes. Confusion in the British headquarters would not allow the numerically superior South Africans to reposition forces from uselessly defending against an amphibious assault, or from the south and west to counter the threat. By nightfall on the 20th, the Germans secured the port.
The next day, the British surrendered. 30,000 Commonwealth troops marched into captivity and it was the second largest surrender in British history after the fall of Singapore some months earlier. In the last six months, the Japanese captured Malaya and Singapore despite being significantly outnumbered, and ignobly ran the British out of Burma with barely better odds. Operation Crusader had six months of dedicated support and priority within the entire British Empire and Rommel erased those painstaking gains in a matter of weeks: first in January, and then in June. The Australians and Poles held Tobruk against all odds for nearly nine months; The British Army gave it away in two days. Any reputation for competence and fighting prowess held by the British Army was gone.
Rommel would tell the captured officers, “Gentlemen, you have fought like lions and been led by donkeys.” He was promoted to Field Marshal shortly thereafter; Rommel was a lieutenant colonel just four years before.
Winston Churchill, in Washington DC meeting with President Roosevelt, called the Fall of Tobruk “a shattering and grievous loss”. He would say to Roosevelt that “I am the most miserable Englishman in America since Burgoyne” (the British general who surrendered at Saratoga during the American Revolution).
Churchill commented in his memoirs that 21 June 1942 was the worst day of World War II.