Why do you think rival forces banded together for mutual defense?

Rival forces often band together for mutual defense due to the recognition that a common threat outweighs their differences. By collaborating, they can pool resources, share intelligence, and strengthen their strategic positions against a more powerful adversary. This pragmatic alliance can help ensure their survival and stability, leveraging their combined strengths to deter or combat the external threat effectively. Ultimately, the urgency of self-preservation can transcend rivalries, fostering cooperation in dire circumstances.