1951: KOREAN WAR/Operation ROUNDUP. To disrupt a new enemy offensive, the U. S. X Corps advances with strong air support near Hoengsong, northeast of Wonju in central Korea. In a 67th Fighter-Bomber Squadron F-51 Mustang, Maj Arnold Mullins shoots down a YAK-9 north of Pyongyang to score the only USAF aerial victory of the month.