The majority of wars are fought over control of territory, not resentment, and the aggressor is almost always either on equal footing or more powerful than the victim. The leaders of a nation won't start a war if they think they could lose it so they must have some materially founded belief that their nation can over power the other (a stronger economy, a more powerful military, a technological advantage). Resentment can be used as a rhetorical tool to motivate hatred of an enemy and to justify an already planned war but it's not the instigating factor.