Political event
Over the course of the near-century, roughly 70 worlds defected from one side to another. There were a myriad of reasons, from ideology to who they thought would win, but the main reason was that a world was far too separated from its central government to get any support in case the other attacked, so defected to gain more security. Towards the end of the period, both states had managed to coerce most of the planets on the fence about whether or not to defect to stay, through a series of bribes, assurances, and threats that they would attack first.