2015's FRC Stronghold is played by 2 alliances of 3 teams. Each alliance competes against each other, their objective is to breach their opponents defenses, their outer works, and capture the tower. To score points the alliance has the option of crossing elements of their opponents' outer works, score the boulders in opponents' tower goal, and either surrounding or hanging on the tower itself. There are a total of five defenses, a secret passage allowing the robot to restock on boulders. In each set in defense there will always be a low bar, 3 selected by alliance, and the last is chosen by the audience. Each match starts with a 15 second autonomous period, then 2 minutes of driver control for the teams to breach the outer works and score as much as they can.