revision preference src: It began being used in 1971 and eventually replaced all other anti-aircraft weapons in the British Army. <SEP> It replaced both guns for targets that were flying low down, and the English Electric Thunderbird which was used against targets that were higher up and further away. <SEP> tgt: Entering service in 1972, it eventually replaced all other anti-aircraft weapons in Army service; both the Bofors guns used against low-altitude targets and the Thunderbird missile used against longer-range and higher-altitude targets.