Start an Easy 'Hot Seat' mode with four players (all on one controller), so you can also unlock All for One.... In a four player game, you win once someone reaches 1,700, so you can technically only get four of the six Territory achievements in this game.
Start each player on different continents. Each player will start with three territories randomly placed around the map. The trick here is to get all the territories in one region (i.e. North America, Europe, etc.) with any player. It doesn’t have to be Player 1 that gets it, since technically, all the players are on your profile. If any of the four players obtain all six territories in one region, the achievement will unlock.
Since the game ends when someone reaches 1,700 points, you can only get one region per player. Save the last two for the second, two-player game, see Hearts and Minds
In ONE game of Explorer mode. You must conquer and take control of all 6 African Territories, 6 Australian-Asian Territories, 6 European Territories, 6 Asian Territories, 6 North American Territories, 6 South American Territories. Once all 6 territories are controlled, the continent will be lock down to the rest of that game and will not be able to be captured by another player.