The conquest of British Malaya and the Dutch East Indies in early 1942 opened the door for Japanese advances into the Indian Ocean. The Vichy French-controlled island of Madagascar stood astride the line of communication between India and the UK and the British were worried that the French would accede to occupation of the island as they had to the Japanese occupation of French Indochina in 1940. Preventing this required a preemptive invasion of Diego Suarez scheduled for May 1942. "Illustrious" had her work up cut short on 19 March to prepare to join the Eastern Fleet in the Indian Ocean and participate in the attack. She sailed four days later, having embarked twenty-one Swordfish, nine Martlet IIs of 881 Squadron and six Martlet Is of 882 Squadron, and two Fulmar fighters prior to escorting a troop convoy carrying some of the men allocated for the assault. A hangar fire broke out on 2 April that destroyed 11 aircraft and killed one crewman, but failed to cause any serious damage to the ship. Repairs were made in Freetown, Sierra Leone, where her destroyed aircraft were replaced and augmented by twelve additional Martlet II fighters from HMS "Archer", while two Martlet I aircraft were, in turn, transferred to "Archer", bringing "Illustrious"s total aircraft complement to 47. After her stay at Freetown, "Illustrious" proceeded to Durban; during the voyage her staff also fitted ASV radar to the replacement Swordfish. One Martlet I was fitted with folding wings.