The Seventeenth Corps under General J. B. McPherson, and the Fifteenth, under General William Tecumseh Sherman, had followed the Thirteenth Corps from Milliken's Bend. Sherman, with his train, arrived at Grand Gulf on the 7th, and the advance was resumed, the line of march being along the Big Black River toward the Vicksburg & Jackson railroad. The goal was to cut off the Jackson forces which Grant had reason to believe were assembling there to move to Pemberton's assistance.
Saturday, May 9, 1863
General Joseph E. Johnston came to Jackson, the Mississippi state capital, and established his headquarters there. Johnston had under his immediate command ten to fifteen thousand troops. Preventing the merger of these with the force under General Pemberton at Vicksburg became an immediate objective for General Grant.
