I do not really find that surprising. The way I think about the observation is as an iterated prisoners dilemma, in which both sides have a history of defect. To expand a bit, wars happen when both sides prefer war to the terms of peace (and in this game theoretic view "terms of peace" does not include any assumption of reasonability, for one side "terms of peace" may well be getting annihilated), plus of course a breakdown of trust. So each side has to prepare for the defection of the other side and neither side trusts that the other side will stick to the cease fire, and has therefore an incentive to attack first.