In War of the 3 Sanchos 1065-67, the fourth game in the Pocket Campaigns series, you are one of three King Sanchos, fighting for control of castles and towers across Castilla, Navarra, and Aragón. The game is designed for 1-3 players.

All three of the King Sanchos, including any non-player Sanchos, are competing to win by fortifying the castles and towers illustrated on the board (one in each region). Players gain victory points for each castle or tower fortified with their pieces: 3 points for a home castle (2 points in the solo game), 2 points for a neutral castle, and 1 point for a tower. If at any time during the game a Sancho has 10 or more victory points, they win a major victory. If no player achieves this during the game, the Sancho with the most victory points after the last card is played wins a minor victory.

The game is played in rounds. Each player has a turn during each round. At the start of the round, the commander for the round plays a card from their hand. This card indicates the number of command points (CPs) from 1 to 3 that the commander uses during the round, and it also describes the actions that each other player must take on their turn, if possible. The game ends either at any point when a Sancho has 10 or more victory points, or after the final card from all players' hands has been resolved.