In his fight against his father, Cronus, Zeus was aided by allies who were his siblings and had been vomited from his father's stomach. His five siblings and allies were other members of the Greek pantheon such as Hestia, Hera, Hades, Poseidon and Demeter. Aside from his siblings, Zeus also had allies in the form of the Cylopes and Hecantonchires, whom he had released from subterranean imprisonment.
The rebellion of Zeus against Cronus is part of a 10-year series of battles in Greek mythology called the Titanomachy or Titanomachia. In mythology, this battle was fought between the Olympian gods and the Titans for control and dominion over the universe.
The conflict between Zeus and Cronus began due to paranoia on the part of Cronus, who consumed his own children. Cronus was afraid that one of his children would eventually rise up to usurp his rule, just as he did with his father Uranus. Zeus avoided being eaten by Cronus when his mother Rhea managed to switch him with a rock and hid him away to be raised on Crete.
The aftermath of the Titanomachy resulted in a victory for the Olympians, the entrapment of the Titans to Tartarus and the punishment of Atlas, one of Cronus' allies, who was forced to hold up the sky.