Development of the U.S. MGR-1 Honest John Rocket began in 1950, with prototype testing in 1951 and production in 1953, as a replacement for super heavy field artillery pieces that were difficult and time-consuming to emplace. Honest John was a spin-stabilized, one-stage rocket with solid propellant propulsion, using four canted auxiliary rockets behind the warhead and canted fins to create spin stabilization. Its three main components—the rocket motor, fins, and warhead—were assembled and loaded onto a launcher consisting of a 6x6 International Harvester 5-ton truck with a canvas cab top and folding windshield to avoid damage during launching, later modified with a metal cab top to help preserve the launcher. The rocket originally carried a variable-yield nuclear warhead of up to 20 kilotons, later upgraded to 30 kilotons, and it could also carry a high explosive or chemical warhead. An improved and slightly shorter model, the MGR-1B, was introduced in 1960, and Honest John was replaced by the Lance in the early 1970s. The rocket had a diameter of 30 inches, a length of 24 feet 10 inches, a weight of 4,300 pounds, and a range of 23 miles.