In Greek mythology, the Titans were the pre-Olympian gods, the generation of gods preceding the Olympians. They were the children of Uranus (Heaven) and Gaea (Earth) and their descendants. According to Hesiods Theogony, there were 12 original Titans: the brothers Oceanus, Coeus, Crius, Hyperion, Iapetus, and Cronus and the sisters Thea, Rhea, Themis, Mnemosyne, Phoebe, and Tethys. The Titans rebelled against their father, Uranus, and under the leadership of Cronus, they deposed Uranus and set up Cronus as their ruler. However, Zeus rebelled against his father, Cronus, and a struggle ensued between them in which most of the Titans sided with Cronus. Zeus and his brothers and sisters finally defeated the Titans after 10 years of fierce battles, known as the Titanomachia. The Titans were then hurled down by Zeus and imprisoned in a cavity beneath Tartarus. The Titans play a key role in an important part of Greek mythology, the succession myth, which tells how Cronus seized power from his father Uranus and ruled the cosmos with his fellow Titans before being in turn defeated and replaced as the ruling pantheon of gods by Zeus and the Olympians.