A problem of guarding a territory with two invaders and two defenders

A problem of guarding a territory with two defenders and two invaders is formulated and investigated. Favorable regions for the players are introduced in order to analyze this problem qualitatively by dividing the playing space into several regions. First, we consider the possibility of whether both invaders are capable of entering the territory successfully. If this is not possible, then we consider the possibility of whether either one of the invaders is capable of entering the territory, in which case the distance between the territory and the invader not entering the territory is chosen as the payoff. If this is not the case, we consider the sum of the distances between the invaders and the territory as the payoff