sentences:  It was concluded that the small warhead and inaccurate guidance made such an application "pointless".However, in 1965 North Vietnam requested an air-to-surface missile from the Soviet government; the AGM-12 Bullpup had entered service with the US Air Force before the start of the Vietnam War.In April 1965 OKB-134 (later NPO Vympel) started work on this missile under the project name Kh-23, but they had problems developing a guidance system that would work with existing aircraft.