Zeus was not always the ruler of the gods. Actually he's a fourth generation
ruler preceeded by Chaos, Uranus, and his father Cronus. The first, Chaos, was basically the
universe. Not much is known about Chaos. My understanding is that Chaos is just the universe. The
second was Uranus (The Heavens) who was overthrown by his son, Cronus. Uranus was a hateful
ruler. He hated all his children which greatly angered his wife Gaea (Mother Earth).
Cronus overthrew Uranus by cutting off Uranus' genitals and casting them into the sea. The way that
story plays out is that Gaea enticed Uranus to bed with her and when he got close enough, Cronus
came out of hiding and cut Uranus' genitals off with a razor sharp jagged sickle. It is from this
incident that many other deities were born. From the blood that dripped off the genitals came the
Erinyes. When the genitals fell into the ocean, Aphrodite was born from the foamish bubbling of the
ocean. Ok, brief lesson in the Theogony is over. Back to Zeus' history.
Cronus had 6 children of his own with his sister/wife Rhea. Cronus was warned that one of his
children would someday overthrow him, so he swallowed each of the first five children right after birth.
Upon the birth of the sixth, Rhea substituted the child for a stone wrapped in clothing. This sixth
child of course was Zeus. He was hidden in Crete until he was full grown. As an infant, he was
suckled by the goat, Amalthea. When he finally became an adult, he and his mother Rhea devised a
plan to force Cronus to throw up the other five children. Zeus did this by dressing as a cupbearer and
serving Cronus a special elixir created by Zeus' first wife, Metis. Zeus, with the help of his brothers,
sisters, and the hundred arm giants, overthrew Cronus and the Titans after a 10 year war. The final
victory was achieved when Zeus brought into play his trademark lightning bolt. He then banished
Cronus and the rest of the Titans to Tartarus, the lowest region of the underworld.