In August 2013, a launching ceremony for Japan's largest military ship since World War II was held in Yokohama. The 820-foot-long (250 m), 19,500-ton flattop Izumo was deployed in March 2015. The ship is able to carry up to 14 helicopters; however, only seven ASW helicopters and two SAR helicopters were planned for the initial aircraft complement. For other operations, 400 troops and fifty 3.5 t trucks (or equivalent equipment) can also be carried. The flight deck has five helicopter landing spots that allow simultaneous landings or take-offs. The ship is equipped with two Phalanx CIWS and two SeaRAM for its defense. The destroyers of this class were initially intended to replace the two ships of the Shirane class, which were originally scheduled to begin decommissioning in FY2014.

Answer this question, if possible (if impossible, reply "unanswerable"): How long is Japan's largest military ship?
820-foot-long (250 m)