In April 1862, Union victories at Shiloh and on the Mississippi River made Confederate control of the river in Tennessee more difficult, and Southern soldiers evacuated posts they could not defend easily, including Memphis. Capt. James E. Montgomery remained with eight gunboat-rams to protect the city. Shortly before dawn on June 6, Federal Capt. Charles H. Davis's ironclad gunboat flotilla and Col. Charles Ellet's Ram Fleet steamed downriver to attack them as Memphis civilians lined the bluffs to watch. After ineffective shelling, the USS rams Queen of the West and Monarch rammed and disabled CSA General Lovell and General Price, and the fighting became one-sided. By mid-morning, all but one of Montgomery's vessels had been destroyed or captured, hundreds of Confederate sailors had been killed or taken prisoner, and Ellet, the only Union fatality, died of his wound two weeks later. The mayor of Memphis surrendered the city to Ellet's son, Medical Cadet Charles R. Ellet, and two marines. On April 27, 1865, about 8 miles north of Memphis, the overloaded side-wheel steamboat Sultana, carrying almost 2,500 persons, mostly newly released Union prisoners of war, suffered a boiler explosion, burned, and sank after leaving Vicksburg; an estimated 1,800 people died in the largest maritime disaster in American history.