The Graf Zeppelin-class aircraft carriers were four German Kriegsmarine aircraft carriers planned in the mid-1930s by Grand Admiral Erich Raeder as part of the Plan Z rearmament program after Germany and Great Britain signed the Anglo-German Naval Agreement. They were planned after a thorough study of Japanese carrier designs. German naval architects ran into difficulties due to lack of experience in building such vessels, the situational realities of carrier operations in the North Sea and the lack of overall clarity in the ships' mission objectives.