Tobruk was an important strategic factor in the conquest of Eastern Libya during World War 2 (WW2)
Italian forces invaded Egypt in November of 1940 and sat just across the border in neatly organized camps along the Mediterranean. The British forces, mainly the 7th Armoured Division, a British and an Indian Infantry Division, launched a counterstrike codenamed Operation COMPASS] in early December.
Italy called on Germany which, under Generalleutnant (later Field Marshal) Erwin Rommel drove the British back across Cyrenecia to Tobruk, laying siege to it until June 21, 1942 when Allied forces surrendered. Tobruk was recaptured on November 11.