Uncas was born near the Thames River in present-day Connecticut, the son of the Mohegan sachem Owaneco. Uncas is a variant of the Mohegan term Wonkus, meaning "Fox". He was a descendant of the principal sachems of the Mohegans, Pequots, and Narragansetts. Owaneco presided over the village known as Montonesuck. Uncas was bilingual, learning Mohegan and some English, and possibly some Dutch.

In 1626, Owaneco arranged for Uncas to marry the daughter of the principal Pequot sachem Tatobem to secure an alliance with them. Owaneco died shortly after this marriage, and Uncas had to submit to Tatobem's authority. Tatobem was captured and killed by the Dutch in 1633; Sassacus became his successor, but Uncas felt that he deserved to be sachem.

Owaneco's alliance with Tatobem was based upon a balance of power between the Mohegans and Pequots. After the death of Owaneco, the balance changed in favour of the Pequots. Uncas was unwilling to challenge the power of Tatobem; however, Uncas did begin contesting Pequot authority over the Mohegans. In 1634 with Narragansett support, Uncas rebelled against Sassacus and Pequot authority. Uncas was defeated and became an exile among the Narragansetts. He soon returned from exile after ritually humiliating himself before Sassacus. His failed challenges resulted in Uncas having little land and few followers, but Uncas saw that the newly arriving Puritan colonists, though few in number, had better weapons and much courage, so he started to develop a new strategy and alliance to work towards his ultimate goal of Grand Sachem.
Given this paragraph about Chief Uncas, who was he?
Uncas (c. 1588 – c. 1683) was a sachem of the Mohegans who made the Mohegans the leading regional Indian tribe in lower Connecticut, through his alliance with the New England colonists against other Indian tribes.