The US Army Air Force recognized the significance of using civilian training aircraft as forward observation platforms during World War II. In response to a request for a modern liaison aircraft in 1949, Cessna developed the Model 305 by combining the wings of its C-170 and the tail surfaces of a C-195 with a newly designed fuselage. This aircraft, later named the Bird Dog and designated as the L-19, was swiftly deployed in combat during the Korean War. A decade later, it was re-designated as the O-1 and equipped with 2.75-inch smoke rockets under each wing. In the Vietnam War, the Bird Dog played a crucial role for the US Army as an artillery spotter. Following a dispute with the Army, the US Air Force also inherited a number of O-1s and incorporated them into their forward air control (FAC) mission.