In A Princess of Mars, with the help of the newly arrived John Carter from Earth, Tars Tarkas becomes a Jeddak (king) of the Tharks.
Thark is a Green Martian tribe and kingdom, whose name comes from the deserted city they have occupied as their capital.
On the one hand, they, like all Greens, are warlike and cruel, and under the reign of Tal Hajus, there were serious considerations about the effectiveness of rape as a tactic for demoralizing female captives.
After Tal Hajus was killed by Tars Tarkas, and with the advice of the Earthman John Carter, the Tharks entered a new age in which base cruelty took a back seat to more diplomatic means for gaining resources.
It was among the Tharks that John Carter earned his earliest honors and met the princess Dejah Thoris.