Once the Axis forces had been defeated in Tunisia, the Allied strategic bomber force commenced attacks on the principal airfields of Sardinia, Sicily and southern Italy, industrial targets in southern Italy and the ports of Naples, Messina, Palermo and Cagliari (in Sardinia). The attacks were spread to maintain uncertainty as to the next Allied move, and to pin down Axis aircraft and keep them away from Sicily. Bombing of northern Italy (by aircraft based in the UK) and Greece (by aircraft based in the Middle East) was increased. From 3 July, bombing concentrated on Sicilian airfields and Axis communications with Italy, although beach defences were left alone, to preserve surprise as to where the landings would occur. By 10 July, only two airfields in Sicily remained fully operational and over half the Axis aircraft had been forced to leave the island. Between mid-May and the invasion, Allied airmen flew 42,227 sorties and destroyed 323 German and 105 Italian aircraft, for the loss of 250 aircraft, mostly to anti-aircraft fire over Sicily.