Korean War two years of fighting became a war of attrition, with the front line close to the 38th parallel. The war in the air, however, was never a stalemate. North Korea was subject to a massive bombing campaign. Jet fighters confronted each other in air-to-air combat for the first time in history, and Soviet pilots covertly flew in defense of their communist allies. The fighting ended on 27 July 1953, when an armistice was signed. The agreement created the Korean Demilitarized Zone to separate North and South Korea, and allowed the return of prisoners. However, no peace treaty was ever signed,
Soviet Union in the Korean War China. By April 1950, the Soviet Union had provided 63 of the North Korean Air Force's 178 aircraft, which until September 1950 proved highly effective against minimal South Korean air defenses (which was more heavily backed by US and UN air forces instead) An important area in which Soviet intervention was key in the Korean War was in the air-war. Soviet innovation in aircraft design, as well as the experience of many of its pilots following the Second World War meant that the 'new' states of China and North Korea were dependent on Soviet help in this area. Both the