machine gun, the M1918 .30 BAR and the P17 .30 Enfield rifle. M1917 Enfield rifles chambered for .303 British were also provided by the U.S. while all .30-caliber U.S. rifles, BARs and machine guns were chambered for .30-06 Springfield Later, the M1919 .30 machine gun and the M2HB .50 machine gun chambered in .50 BMG were provided by the U.S. for infantry and anti-aircraft use. Browning AN2 light machine guns in .303 British caliber were already in standard use on British aircraft beginning in the late 1930s. Britain supplied small arms to the USSR, and the 9mm Sten submachine gun was supplied to Soviet partisan troops. Artillery The British made use of many American towed artillery pieces during the war, such as the M2 105 mm howitzers, M1A1 75mm Pack Howitzers, 155 mm guns (Long Toms). These weapons were supplied under Lend-Lease or bought outright. Tank/tank destroyer guns used by the British included the 37 mm M5/M6 Gun (General Stuart and General Grant/Lee tanks), 75mm M2 Gun (General Grant/Lee), 75 mm M3 Gun (General Grant/Lee and General Sherman), 76 mm Gun M1 (General Sherman) and 3" Gun M7 (3in SP M10). The Americans in turn used a British artillery piece, the Ordnance QF 6-pounder 7cwt anti-tank gun. The US realized at the start of the war that their own 37 mm Gun M3 would soon be obsolete and thus they produced a license built version of the QF 6-pounder under the designation 57 mm Gun M1. Both 76 mm and 75 mm guns were mounted on tanks sent to the Soviets by the US, while the British tanks sent were armed with both the Ordnance QF 2-pounder and the Ordnance QF 6-pounder. Another technology taken to the US, by Henry Tizard, for further development and mass production, was the (radio-frequency) proximity fuse. It was five times as effective as contact or timed fuzes and was devastating in naval use against Japanese aircraft and so effective against German ground troops that General George S. Patton said it "won the Battle of the Bulge for us." Tanks and other vehicles The Medium Tank M4 was used in all theatres of the Second World War. It had a versatile reliable design and was easy to produce, thus huge numbers were made and provided to both Britain and the USSR by the United States under Lend-Lease. Despite official opinions, the Medium Tank M4 was