During the American Civil War, the city finally surrendered during the Siege of Vicksburg, after which the Union Army gained control of the entire Mississippi River. The 47-day siege was intended to starve the city into submission. Its location atop a high bluff overlooking the Mississippi River proved otherwise impregnable to assault by federal troops. The surrender of Vicksburg by Confederate General John C. Pemberton on July 4, 1863, together with the defeat of General Robert E. Lee at Gettysburg the day before, has historically marked the turning point of the Civil War in the Union's favor.