The Second World War campaign in north-eastern India and northern Burma was fought in jungle and mountains with few or non-existent roads and which facilitated the infiltration of enemy patrols behind front lines. This was overcome by holding defensive "boxes" mainly or entirely supplied by air. The defence of forward airfields close to the main army concentrations was vital to this tactic. A training school and depot for the RAF Regiment was established at Secunderabad in October 1942, to retrain former ground defence airmen. It had an assault course considered tougher than anything the army had in India. Six field squadrons and seventy AA flights were initially formed, containing 160 officers and 4,000 other ranks. Until mid-1944 the AA flights were equipped only with light machine guns, then with Hispano 20 mm cannon for the rest of the war. Regiment units defended airfields and forward mobile radar units in Arakan in the Arakan Campaign in late 1942 and early 1943.