Paul Kennedy reports that in World War I, when the Japanese were allied with the UK, they patrolled the Indian Ocean at the request of Britain. They also "dispatched a dozen destroyers for anti-submarine work in the Mediterranean," he notes.
Nor did I know that in the German defense plan of 1938 called for it to build four aircraft carriers.
Finally, I learned that during World War II, more German U boats were sunk by Allied aircraft (288) than by surface ships (246). (Another bunch were deep-sixed by combined actions.)
Thomas E. Ricks covered the U.S. military for the Washington Post from 2000 through 2008. He can be reached at firstname.lastname@example.org.