In many social species, from hymenoptera to primates, group members contribute to repel outsiders. Which group members get involved into the repulsion and at what level of involvement is not yet fully understood; sometimes sub-ordinates (helpers) sacrifice themselves in the action and at other times, group members refuse to assist their breeders. Repellent actions are costly, both for the individual and the dependent young, and there might be a point when winning a contest requires that much involvement that the fitness return from winning is lower than the fitness return from losing the contest without getting involved in the first place. This point can differ among group members and thus, the interests in how much and how long effort is spent in a contest can clash within the group. We calculate the inclusive fitness of each group member and identify when the interests of group members over getting involved into a contest with an outsider diverge and thus, when within-group conflict is likely to occur.