Communist forces were principally armed with Chinese and Soviet weaponry though some Viet Cong guerrilla units were equipped with Western infantry weapons either captured from French stocks during the first Indochina war or from ARVN units or requisitioned through illicit purchase. The ubiquitous Soviet AK-47 was widely regarded as the best assault rifle of the war and it was not uncommon to see U.S. special forces with captured AK-47s. The American M-16, which replaced the M-14, was considered more accurate and was lighter than the AK-47 but was prone to jamming. Oftentimes the gun suffered from a jamming flaw known as “failure to extract,” which meant that a spent cartridge case remained lodged in the chamber after a bullet flew out the muzzle. This caused serious problems during firefights. Jamming problems were generally associated with poor maintenance but these problems were remedied with the issuance of cleaning kits and better maintenance. The heavily armored, 90mm M48A3 Patton tank saw extensive action during the Vietnam War and over 600 were deployed with US Forces. They played an important role in infantry support though there were few actual tank versus tank battles. The M67A1 flamethrower tank (nicknamed the Zippo) was an M48 variant used in Vietnam. Artillery was used extensively by both sides but the Americans were able to ferry the lightweight 105mm M102 howitzer by helicopter to remote locations on quick notice. With its 17 mile range, the Soviet 130mm M-46 towed field gun was a highly regarded weapon and used to good effect by the NVA. It was countered by the long-range, American 175mm M107 Self-Propelled Gun. The United States had air superiority though many aircraft were lost to surface-to-air missiles and anti-aircraft artillery. U.S. air power was credited with breaking the siege of Khe Sanh and blunting the 1972 Communist offensive against South Vietnam. At sea, the U.S. Navy had the run of the coastline, using aircraft carriers as platforms for offshore strikes and other naval vessels for offshore artillery support. Offshore naval fire played a pivotal role in the Battle for the city of Hue, providing accurate fire in support of the U.S. counter-offensive to retake the city. The Vietnam War was the first conflict that saw wide scale tactical deployment of helicopters. The Bell UH-1 Iroquois was used extensively in counter-guerilla operations both as a troop carrier and a gunship. In the latter role, the “Huey” as it became affectionately known, was outfitted with a variety of armaments including M60 machineguns, multi-barreled 7.62mm Gatling guns and unguided air-to-surface rockets. The Hueys were also successfully used in MEDEVAC and search and rescue roles.