"In 1949, Louis A. Johnson, secretary of the newly created Department of Defense," - from wikipedia.
The rest of the world was soon to follow suit, renaming their War Offices 'Defence Ministry' in slavish obedience to the American example, but to Britain's credit only after Suez, when American thuggery was made explicit.
Like any mediocrity, the Americans could not abide rivals.
At least the French had the decency to leave NATO.
Of course, this exercise in semantics saw an explosion in US aggression all round the world, cold when possible but hot when required.
Lots of fun was had. It was a big adventure. I don't know which semantic acrobatics the Soviets used for their own brand of death-dealing.
But we all thought that it would end when the USSR did; of course it didn't. The beast needed feeding.
And so America projects its power with little restraint, fig leaves being supplied by supine 'allies' like Blair's Britain.
When Britain had a War Office, there were interventions in 1948 and 1956; when we were all supposed to enter the brave new world opened up by the invented crime of 'waging aggressive war', and the name was changed to 'Defence', we had 1958, 1961, 1967, 1968-2000, 1990, 1982, 1999, 2000, 2003, 2001.
And that's just Britain.
At least a War Office does what it says on the tin; malfeasants know that there is a line to be crossed, that we have our fists raised.
Since following the American governmental hypocrisy, there is a game of trickery, where every crime can be justified.
In 2001 the crime was against New York.
In 1939 the crime was falsified, and the Nazis 'defended' themselves the way Bush and Blair defended us against Iraq.
Either these individuals are brought to book as people who waged aggressive war, or we forget the whole charade and go back to War Ministries.