All Military Monkeys get a one-off +1000 XP and earn XP in-game 5% faster permanently.
~ BTD6 description
Elite Military Training is an upgrade in the Military Monkey Knowledge Tree, first released on initial release. It gives all Military Monkeys a one-off +1000 XP, as well making them earn XP in-game 5% faster permanently. Elite Military Training has no knowledge prerequisites.
This Knowledge has no effect if all Military upgrades are already unlocked, besides unlocking subsequent Knowledge.
Newly released Military Monkeys, specifically Mortar Monkey and Dartling Gunner, will earn the one-off 1000 XP bonus as soon as they have been placed on the map for at least one round, provided that this Monkey Knowledge is active.
To make the most of this MK, it should be unlocked early on in the entire game.