"You can’t drop half the sentence and have the same meaning."

In a very technical sense, but if you understand what a subordinate clause means you'll know what can be dropped with changing the restriction on everyone of the main clause.

The technical sense comes from what the subordinate was politically achieving at that time, the Anti-Federalists were properly suspicious of standing armies and regulars, but the guys who actually got a reputation for the successful prosecution of the Revolutionary War starting with the indispensable man Washington knew the nation's defense could not entirely be left to militias.