American involvement in the Everglades began during the Second Seminole War (1836–42), a costly and very unpopular conflict. The United States spent between $30 million and $40 million and lost between 1,500 and 3,000 lives. The U.S. military drove the Seminoles into the Everglades and were charged with the task of finding them, defeating them, and moving them to Oklahoma Indian territory. Almost 4,000 Seminoles were killed in the war or were removed. The U.S. military was completely unprepared for the conditions they found in the Everglades. They tore their clothes on sawgrass, ruined their boots on the uneven limestone floor, and were plagued by mosquitoes. Soldiers' legs, feet, and arms were cut open on the sawgrass and gangrene infection set in, taking many lives and limbs. Many died of mosquito-borne illness. After slogging through mud, one private died in his tracks of exhaustion in 1842. General Thomas Jesup admitted the military was overwhelmed by the terrain when he wrote to the Secretary of War in 1838, trying to dissuade him from prolonging the war.