The Lexington-class battlecruisers were officially the only class of battlecruiser to ever be ordered by the United States Navy. While these six vessels were requested in 1911 as a reaction to the building by Japan of the Kongō class, the potential use for them in the U.S. Navy came from a series of studies by the Naval War College which stretched over several years and predated the existence of the first battlecruiser, HMS Invincible (a series of proposed battlecruiser designs was in fact submitted to the General Board in 1909 but was not approved for construction). The fact they were not approved by Congress at the time of their initial request was due to political, not military considerations.