Vicksburg was on 200-foot-high cliffs above the Mississippi River. It would have been extremely difficult to invade. Farragut ordered Vicksburg to surrender. Grant's troops began the Siege of Vicksburg in mid-May of 1863. They cut off the city and shelled it. People had to eat dogs, horses, and rats due to low food supply. Confederate troops sent a warning to their commander saying that they will rebel unless the commander surrenders and they get fed. On July 4, Commander Pemberton surrendered.