US Military records were not kept prior to 1968, in Vietnam. 3,747 war dogs (officially designated military working dogs during the war) are documented as having served in South Vietnam. Estimates run over 5,000 canines. 10,000 US servicemen operated as dog handlers in South Vietnam during the war: 65% were used by the USA; 26% by the USAF; 7% by the USMC; and 2% were used by the USN. 73 dog handlers and 43 K9's were killed in Vietnam.