When the Pilgrims arrived at Plymouth in 1620 and established the first permanent English settlement in New England, they encountered a Native American population in profound crisis. Just four years earlier, diseases introduced by previous European visitors had wreaked havoc, cutting the local Indian population from an estimated fifteen thousand to no more than one thousand. The Pilgrims constructed their settlement on the site of a recently depopulated village. The Wampanoag Indians, a local confederation of several dozen villages led by the sachem Massasoit, faced military as well as demographic catastrophe. While their Indian allies also had been decimated by disease, their bitter enemies were unharmed. In desperation, the Wampanoag entered an alliance with the Pilgrims, celebrating the new relationship a year later in what has come to be known as the first Thanksgiving. Over the following decades, Plymouth and other English colonies used the alliance to seize additional Indian lands and build their regional power, while the Wampanoag used it to protect their own territories, dominate their Indian rivals, and enrich themselves through trade.