Doubling

Doubling is the term which players use when two players, usually yourself and your ally attack one player at one time. Doubling can used to a players advantage since you can attack the attacking players bases while they are doubling your ally. Professional players will make a good defence in their base before they decide to double their opponent. This strategy is used many levels like Pressure_Point and Face_Off to either finish a player off at the end of the game or to damage their opponent at the start of the game to give them the upper edge in the game.

Doubling is a strategy and should be taken as so, It isn't against any rules as long all players decided to allow before/during the game.