The siege of Tobruk () took place between 10 April and 27 November 1941, during the Western Desert campaign (1940–1943) of the Second World War. An Allied force, consisting mostly of the 9th Australian Division, commanded by Lieutenant-General Leslie Morshead, was besieged in the North African port of Tobruk by German and Italian forces. The tenacious defenders quickly became known as the Rats of Tobruk. After 231 days, they were finally relieved by the British Eighth Army.
In late 1940, the Allies had defeated the Italian 10th Army during Operation Compass (9 December 1940 – 9 February 1941) and trapped the remnants at Beda Fomm. On 22 January 1941, Tobruk's Italian garrison surrendered. But in early 1941, much of the British Western Desert Force was sent to the Greek and Syria–Lebanon campaigns, leaving only a skeleton force short of equipment and supplies.
Adolf Hitler felt compelled to send reinforcements, commanded by Generalleutnant Erwin Rommel, to rescue his beleaguered Italian ally. Rommel launched Operation Sonnenblume (6 February – 25 May 1941), driving the Allies back across Libya to the Egyptian border. However, Tobruk held out, depriving Rommel of a supply port closer to the Egyptian–Libyan border than Benghazi, 560 mi (900 km) west of the Egyptian frontier. The Axis siege of Tobruk began on 10 April and continued despite two failed Allied relief attempts: Operation Brevity (15–16 May) and Operation Battleaxe (15–17 June). The garrison repulsed several Axis attacks. The port was frequently bombarded by artillery, dive-bombers and medium bombers, while the Royal Air Force flew defensive sorties from airfields far away in Egypt. Allied naval forces, such as the British Mediterranean Fleet (including the Inshore Squadron) ran the blockade, carrying reinforcements and supplies in and the wounded and prisoners out. Finally, Operation Crusader (18 November – 30 December) succeeded in raising the siege.
The Western Desert Campaign was fought from Mersa Matruh in Egypt to Gazala in Cyrenaica on the Libyan coast, an area about 390 kilometres (240 mi) wide along the Libyan Coastal Highway (Italian: Via Balbia), the only paved road. A sand sea 150 mi (240 km) inland marked the southern limit of the desert, which was at its widest at Giarabub and Siwa; in British parlance, the Western Desert came to include eastern Cyrenaica in Libya. Extending inland from the coast lies a raised, flat plain of stony desert, about 500 ft (150 m) above sea level, for 120–190 mi (200–300 km) to the sand sea. Scorpions, vipers and flies populated the region, which was inhabited by a small number of nomads. Bedouin tracks linked wells and the more easily traversed ground; navigation was by sun, star, compass and "desert sense", good perception of the environment gained by experience. When Italian troops advanced into Egypt in September 1940, the Maletti Group got lost leaving Sidi Omar and had to be found by aircraft.
In spring and summer, days are hot and nights cold; the sirocco, a hot desert wind blows clouds of fine sand, which reduces visibility to a few metres and coats eyes, lungs, machinery, food and equipment; motor vehicles and aircraft need special oil filters and the barren ground means that supplies for military operations have to be transported from outside. German engines tended to overheat and tank engine life fell from 1,400–1,600 mi (2,300–2,600 km) to 300–900 mi (480–1,450 km), which was made worse by the lack of standard parts for German and Italian types. The ground is a hard surface which drops to sea level in steps, with the coast cut by ravines.
The Italian fortifications at Tobruk included an outer perimeter, comprising a double semi-circle of dug-in strongpoints with concrete walls, positioned well for forward observation, an inner anti-tank ditch, some parts of which were behind barbed wire and/or included booby traps, as well as several more fortified positions closer to the port, at the Bardia–El Adem road junction and towards Fort Pilastrino.
In January 1941, the British XIII Corps, under the command of Lieutenant-General Richard O'Connor, surrounded Tobruk as part of Operation Compass. The fortress was defended by the Italian XXII Corps, commanded by General Enrico Pitassi Mannella.
After blockading the port for a fortnight, the Royal Navy, led by the monitor HMS Terror under the command of Captain Hector Waller, bombarded the defenses on the night of 20 January. Destroyers maintained a screen further out to intercept the cruiser San Giorgio should it attempt a breakout. On the morning of 21 January, British artillery bombarded the town from 05:00 to 07:00. At 07:00, the 2/3rd Australian Infantry Battalion attacked, rapidly breaching the perimeter; by evening, nearly half of the Italian defenses had fallen. The following day, the naval command surrendered. By 16:00, the remaining Italian forces under General della Mura surrendered, General Pitassi Mannella having been taken prisoner earlier that morning.
In February of 1941, the Allies defeated the 10th Army and the 5° Squadra of the Regia Aeronautica, after which Allied leaders decided to hold the area with minimal forces and send the remainder of the WDF to Greece. The Australian 9th Division and the British 2nd Armoured Division (Major-General Michael Gambier-Parry), minus a brigade group sent to Greece, were left to garrison Cyrenaica under Cyrenaica Command (Cyrcom: Lieutenant-General Henry Maitland Wilson), despite the inadequacy of the force if the Germans sent reinforcements to Libya. Command in Egypt was taken over by Lieutenant-General Richard O'Connor and the XIII Corps HQ was replaced by the HQ of the 1st Australian Corps (Lieutenant-General Thomas Blamey). It was believed by General Wavell and the GHQ in Egypt that the Germans could not attack until May, when the 9th Australian Division, two more divisions and support troops, particularly artillery would be ready and the tanks of the 2nd Armoured Division would have been overhauled.
The 2nd Armoured Division had a reconnaissance regiment and the 3rd Armoured Brigade (Brigadier Reginald Rimington), which had an under-strength light tank regiment and one equipped with captured Fiat M13/40 tanks. The cruiser tank regiment arrived in late March with worn-out tracks, after many breakdowns en route and brought the division up to an under-strength armoured brigade. Most of the British tanks were worn out and the Italian tanks were slow and unreliable. The British 2nd Support Group (similar to a small infantry brigade) had only a motor battalion, a 25-pounder field gun regiment, an anti-tank battery and a machine-gun company. The division was short of transport and its workshops were understaffed and lacked spare parts. Two brigades of the 9th Australian Division (Major-General Leslie Morshead) were swapped with two from the 7th Australian Division (Major-General John Lavarack), which had insufficient training, equipment and transport.
Lack of transport made it impossible to supply a garrison west of El Agheila, the most favourable position for a defensive line and restricted the 2nd Armoured Division to movement between supply dumps, reducing its limited mobility further. In February, Lieutenant-General Philip Neame took over Cyrcom and predicted that the armoured division would lose many tanks through breakdowns if it had to move far. Neame asked for a proper armoured division, two infantry divisions and adequate air support to hold the area; he was told that there was little to send and none of that before April. In early March, the 9th Australian Division began to relieve the 6th Australian Division (Major-General Iven Mackay) at Mersa Brega for shipment to Greece, which demonstrated the difficulty of tactical moves with insufficient transport and it was withdrawn to the area east of Benghazi.
Neame was ordered to conserve the tank units, retire as far as Benghazi if pressed, abandon it if necessary, and hold the high ground nearby for as long as possible, with no prospect of reinforcement before May. Neame was to fight a delaying action up the Via Balbia towards Benghazi and then the defiles near Er Regima and Barce; the tanks would move to Antelat to operate against the flank and rear of an attacker moving up the road or across the desert to Tobruk, falling back on a flank if necessary. On 20 March, the 2nd Armoured Division took over from the Australians, who moved back to Tocra, near Er Regima. The force was to use depots at Msus, Tecnis, Martuba, Mechili and Tmimi, El Magrun and Benghazi as a substitute for lorry-borne supply. The 3rd Indian Motor Brigade (Brigadier E. W. D. Vaughan) arrived in late March, with lorries but no tanks, artillery, anti-tank guns and only half its wireless sets; the brigade was based at Martuba, ready to use its vehicles to move towards Derna, Barce or Mechili.