In the fall of 1540, Hernando de Soto brought a 700-man army into Alabama as part of the first major European expedition to the interior of the southeastern United States. After landing at Tampa Bay, Florida, in the spring of 1539, the expedition traveled through parts of Florida, Georgia, North and South Carolina, Tennessee, Alabama, Mississippi, Arkansas, Louisiana, and Texas before abandoning its search for riches and leaving for Mexico in 1543. Archaeologists believe they know the expedition's general route and continue trying to identify the specific towns it visited. In Alabama, the expedition likely entered near Piedmont, traveled down the Coosa River Valley to Montgomery, then moved west and north, leaving the state by crossing the Tombigbee River near Columbus, Mississippi. Probably near present-day Montgomery, de Soto met the Indian chief Tascalusa, who, resentful of harsh Spanish treatment of Indians, promised supplies and bearers at Mabila. There, on October 18, 1540, Tascalusa ambushed de Soto's advance party after it entered the town. De Soto summoned his main force and fought an all-day battle in which more than 20 Spaniards and 2,500 Indians were killed, in what has been called the greatest Indian battle ever fought in America. Although the Spaniards prevailed, the battle marked the turning point of the expedition: de Soto found no gold or silver, suffered major casualties, continued slowly toward Mississippi, and over the next three years the expedition discovered the Mississippi River, lost de Soto to fever, and saw about 300 survivors retreat to Mexico. The expedition's four principal accounts provide some of the best insights into the life and customs of the Indians of the Southeast before the impact of European civilization. The exact route through the Southeast remains uncertain because the expedition left little physical evidence and did not record accurate latitude and mileage measurements. A 1939 United States De Soto Commission report proposed an official route, and later archaeological work, including study of more than 300 Indian sites in Alabama, led many scholars to favor the route advanced by Dr. Charles Hudson and his associates, especially from near Piedmont down the Coosa River Valley into the Montgomery-Selma area, though debate continues beyond that point.