Vicksburg was the site of a seemingly impregnable fortress that governed the passage of shipping on the Mississippi River. Grant's goal there was to gain control of the river and thereby sever the western Confederacy. In approaching the fortress, he found that his army could live off the land. Photographers recorded his progress into the Deep South. "I was amazed at the quantity of supplies the country afforded," Grant wrote. Not many commanders would have been willing to cut their supply lines in enemy territory.