For winning a game of Warzone on all 3 of the original maps. They are;
Escape from A.R.C
March On Stormbreak
Raid On Apex 7
You must play original Warzone, not a variant. You can check your stats in game to see which maps you've won on. Points are earned by controlling any of the 3 areas, as well as kills. Killing enemy AI bosses is worth a lot of points, and can quickly turn a game, so they should be prioritized. Games go to 1000 points, or if a team controls all 3 areas, they can then enter the enemy's base and destroy their Core, finishing the game instantly. There is no time limit, and games can take anywhere up to 1/2 hr to complete. Achievement should pop as soon as you get the win on your 3rd map.