> To your latter point, the US became significantly more bellicose after the War Department became the Defense Department (merged with the Navy Department).
Did we?
After independence, we spent about a century engaged in war with native tribes until they'd effectively been wiped out. The conflicts spanned from Florida to California, Texas to the Dakotas.
We invaded and annexed half of Mexico. We attempted to invade Canada in the War of 1812. We fought in North Africa not long after securing our independence and would do so multiple times.
We were pioneers in industrial total war which we practiced upon ourselves in the Civil War.
We won Cuba, Puerto Rico and the Philippines from Spain in a war that had much flimsier causes than WMDs in Iraq and lacked any semblance of a noble goal.
The Department of Defense came after WWII, and while we've had our fair share of at best misguided wars since then, it's not a recent development.
That's not to say the name isn't Orwellian in nature.