This neatly transcends Einstein's "I do not know with what weapons World War III will be fought, but World War IV will be fought with sticks and stones."

Back off to high earth orbit and drop a big stick on 'em.

The 107-country Outer Space Treaty signed in 1967 prohibits nuclear, biological, or chemical weapons from being placed in or used from Earth's orbit. What they didn't count on was the US Air Force's most simple weapon ever: a tungsten rod that could hit a city with the explosive power of an intercontinental ballistic missile.
https://www.businessinsider.com/air-...n-force-2017-9