In 1961, at age 33, he wrote "Aerial Attack Study," which codified the best dogfighting tactics for the first time, became the "bible of air combat," and revolutionized the methods of every air force in the world.
His Energy-Maneuverability (E-M) Theory helped give birth to the legendary F-15, F-16, and A-10 aircraft.
Perhaps his most significant contribution to military strategy, though, came from a series of briefings he gave. In them, Boyd laid out a way of thinking about conflict that would revolutionize warfare around the world.
The idea centers on an incredible strategic tool: the OODA Loop — Observe, Orient, Decide, Act. Nation-states around the world and even terrorist organizations use the OODA Loop as part of their military strategy. It has also been adopted by businesses to help them thrive in a volatile and highly competitive economy.
Comment: This is why ISIS is a Frankenstein monster. Even if it is or has been controlled or directed by 'higher powers' (e.g., CIA, Turkish/Saudi intel, etc.), it is not simply a mercenary army that will do the bidding of its masters. Mercenaries are only as loyal as their paycheck is reliable. But brainwashed fanatics can't be so easily controlled. Now the world is stuck with them. Ironically, many of the major geopolitical divisions can be healed if all countries sincerely unite their efforts to put an end to international terrorism. And that at least has the chance of happening, if Trump's USA and Putin's Russia collaborate.
The U.S. has never been really serious about fighting terrorism. It's too useful. (See for example: John Kerry admits that Russia entered Syrian war to stop ISIS, U.S. used ISIS to pressure Assad) Russia has always been serious about it, because terrorism has always been a real threat to them. If the U.S. were to get serious, that would be something amazing. But the war would have to be fought on two fronts, which includes purging the American deep state of its own terrorists.