Between 1616 and 1619, infectious diseases killed thousands of Algonquians in coastal areas south of Rhode Island. The Narragansetts were the most powerful tribe in the southern area of the region when the English colonists arrived in 1620, and they had not been affected by the epidemics. Chief Massasoit of the Wampanoags to the east allied with the colonists at Plymouth Colony as a way to protect the Wampanoags from Narragansett attacks. In the fall of 1621, the Narragansetts sent a sheaf of arrows wrapped in a snakeskin to Plymouth Colony as a threatening challenge, but Plymouth governor William Bradford sent the snakeskin back filled with gunpowder and bullets. The Narragansetts understood the message and did not attack them.