The MGR-1 Honest John rocket was the first nuclear-capable surface-to-surface rocket in the United States arsenal.[notes 1] Originally designated Artillery Rocket XM31, the first unit was tested on 29 June 1951, with the first production rounds delivered in January 1953. Its designation was changed to M31 in September 1953. The first Army units received their rockets by year's end and Honest John battalions were deployed in Europe in early 1954. Alternatively, the rocket was capable of carrying an ordinary high-explosive warhead weighing 1,500 pounds (680 kg).