How early did Japan consider a carrier strike on Pearl Harbor?

The suggested origin of a Pearl Harbor carrier strike predates the officers' later claims to have devised it. Japanese naval observers knew about British plans against Wilhelmshaven, the Cuxhaven raid of 25 December 1914, and the Sopwith Cuckoo torpedo aircraft. That experience supports an inference that Japanese officers considered attacks on American installations as their own carrier force developed. Hosho offered different possibilities from the larger Akagi and Kaga, just as Langley differed from later American carriers. The proposed chronology remains an interpretation, rather than a documented date for an approved Pearl Harbor operation. The comparison with British Taranto plans dating from about 1926 illustrates how a contingency could be periodically updated for years. Current intelligence, available aircraft and concentrated staff work would still be needed to make it executable.