The force restructuring wasn't simply to rename the Dept. of War. At the time the Navy was an entirely separate entity headed by its own Cabinet-level Secretary

The force restructuring wasn't simply to rename the Dept. of War. At the time the Navy was an entirely separate entity headed by its own Cabinet-level Secretary. With the introduction of the USAF as a separate service it was decided that instead of having 3 Cabinet-level secretaries all relating to the military, that there would instead be a single military department led by a single Cabinet-level secretary. Each military service would have their own Secretary who reported to this new Secretary of Defense. Since they were restructuring anyways the name change was easy to throw on in the process. Honestly, the name change conformed more to the existing thought of what the military was. Many military actions had been authorized outside of a formal war status since 1798, so the military services were clearly not only about the prosecution of war. That particular change was in fact long overdue.