The campaign to capture the Confederate stronghold at Vicksburg, Mississippi, the last major obstacle to Union control of the Mississippi River, had bogged down in the winter of 1862–1863. The Union's Major General
Ulysses S. Grant had put into motion several operations aiming at flanking Confederate Lieutenant General
John C. Pemberton's fixed defenses. Grant wanted to keep his troops busy until he could begin active campaigning later in the spring, so he ordered them to undertake several moves that would give the appearance of activity but would not bring on a major battle. Writing in his memoirs long after the event, he stated that he did not have great confidence that any of them would prove successful, although he was prepared to take advantage of them if they did. Not only had the operations failed to produce any good results, but the last, the joint Army–Navy operation known as the
Yazoo Pass expedition, was in danger of being captured or destroyed before it could extricate itself from enemy territory. Grant and Acting Rear Admiral
David D. Porter therefore set one more operation in motion. Like the others, it was an effort to get on the enemy flank; it had the additional purpose of relieving some of the pressure on the earlier expedition. To avoid the lethargy in command that had hampered the Yazoo Pass operation, Porter himself went with the gunboats, and the Army was under the personal direction of Major General
William T. Sherman. Grant's orders to Sherman lay out the course of the expedition. They also show that he was not completely sure of its success. "You will proceed as early as practicable up Steele's Bayou and through Black Bayou to Deer Creek, and thence with the gunboats now there, by any route they may take, to get into the Yazoo River for the purpose of determining the feasibility of getting an army through that route to the east bank of that river, and at a point at which they can act advantageously against Vicksburg."
Geography The expedition was very much limited by the geography of the
Mississippi Delta, the flood plain of the river occupying most of northwestern Mississippi. The land is quite low and is in fact lower in many places than the river. The region is characterized by numerous marshes, brakes, sloughs, bayous, lakes, creeks, and rivers that in the geologic past were parts of the river bed. Until the middle of the nineteenth century, overflow from the Mississippi continued to pass into these waters, and they could be used as alternatives to the main river for water transportation. When railroads provided more convenient commerce, however, levees to contain the flow had been built, and the land was partially drained. Then, when the war came, the levee was breached for the Yazoo Pass expedition, and the land was again flooded. Minor waterways swelled to the size of small rivers, raising the possibility that Union gunboats could travel on them. Porter believed that he could send his gunboats and army transports up Steele's Bayou (present-day Steele Bayou) to Black Bayou, into Deer Creek, then Rolling Fork, and finally into the (Big)
Sunflower River. The last met the Yazoo River a short distance upstream from the bluffs where a major
Union attack had been repulsed in late 1862. Porter had to rely on imperfect maps and the advice of local citizens who did not understand the difficulties of moving heavy warships in a narrow channel with numerous bends. He was therefore unprepared for the problems presented by Deer Creek. There the straight-line distance between the entry point at Black Bayou and the exit at Rolling Fork, , was only half the distance along the creek, . He was also unaware of the impedance to mobility imposed by the overhanging trees that grew down to the water's edge and by the submerged vegetation that seized the hulls of his vessels. When encountered, these problems limited progress of the gunboats to as little as every two hours. ==Start of the expedition and Confederate response==