Why did towns band together under the leadership of a king in city states?

Towns banded together under the leadership of a king in city-states primarily for mutual protection and to enhance their collective security against external threats. This unification also facilitated trade and resource sharing, fostering economic growth and stability. Additionally, centralized leadership helped establish laws and governance, promoting social order and cooperation among the towns. Ultimately, this alliance under a king aimed to create a stronger, more cohesive political entity.