The Pequot War was the first major conflict between Native Americans and Europeans in northeastern North America. It began in September 1636, lasted eleven months, and involved thousands of Native and English peoples who fought several major battles in present-day Connecticut. In the early months of the war, most fighting occurred around Saybrook Fort, where the Pequot quickly laid siege after a Massachusetts Bay force attacked Block Island and then burned Pequot villages in retaliation for the 1634 killing of trader John Stone, while the Pequot were wrongly blamed for the 1636 killing of Captain John Oldham off Block Island. Lieutenant Lion Gardiner defended Saybrook Fort through the fall and winter of 1636-1637 against repeated attacks, even as over half the garrison became casualties and by spring 1637 only a dozen men remained. The siege was lifted in early March 1637 when reinforcements from Massachusetts Bay under Captain John Underhill arrived and the English-allied Narragansett attacked Pequot territory from the east. Saybrook Fort then became the main gathering and staging place for English campaigns against the Pequot at Mistick and Quinnipiac, including the attack on the Pequot fort at Mistick that became the war's turning point. The war grew from rapid cultural, political, and economic change after Dutch fur traders arrived in 1611; in the 1620s and early 1630s the Pequot dominated the fur and wampum trade along Long Island Sound and the lower Connecticut River Valley, but English settlement in the fall of 1633 challenged Dutch and Pequot influence. Before the war, about 8,000 Pequot lived in territory now defined by Groton, Ledyard, Stonington, and North Stonington, but a smallpox epidemic in the early 1630s reduced their population to 4,000. After the war, Saybrook Fort remained in use until fire destroyed it in 1647.