Between the World Wars, purpose built trainers covering a variety of specialties largely replaced obsolete types in the Western armed forces, including aircraft specifically for bombing and gunnery and navigational training. When Germany began rearming in the 1930s, many of the initial aircraft were designed with a dual role, so that when they were obsolete in their combat role they would be used as trainers. By WW2 however their needs exceeded what could be spared from production and although using a number of purpose built designs such as the Bücker Bü 131, relied largely on captured aircraft and obsolete combat types.