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The authors study conflict on multiple fronts. A defending player needs to successfully defend all fronts, and an attacker needs to win at only one. Multiple fronts result in a considerable disadvantage for the defending player, and even if there is a defense advantage at each of them, the payoff of the defending player is zero if the number of fronts is large. With some positive probability, in the equilibrium defending players surrender without expending effort.
Clark et al. (2007) studied this question.