The Battle of the Atlantic was fought around merchant ships carrying supplies to and from the British Isles. While HX convoys, ON convoys, SC convoys, and CU convoys sailed to or from North America, Gibraltar convoys carried supplies on the traditional trade route with the remainder of the British Empire through the Mediterranean Sea, Suez Canal, Red Sea, and Indian Ocean. Proximity to Francoist Spain and Fascist Italy made this traditional trade route vulnerable to hostile observation and interception. Protection of this shipping route was similarly important to France for trade with colonial North Africa, Syria, Lebanon, Madagascar, and Indochina. Gibraltar convoys were escorted by French warships until the surrender of France. Most shipping to and from the Indian Ocean and eastern Mediterranean was diverted around Africa until the surrender of Italy. OG and KM convoys consisted largely of supplies for the military garrisons and civilian populations of Gibraltar and Malta, and for Operations Torch and Husky. The proximity of this convoy route to U-boat bases in occupied France caused frequent overlap of convoy battles with Allied offensive patrols in the Bay of Biscay. Air cover was flown from Cornwall and Gibraltar when conditions allowed; but an "air gap" remained where U-boats and surface raiders could patrol the convoy routes unobserved until air patrols began flying from the Azores in October 1943.