To support the army's push inland, Grant established a base on the Mississippi River
at Grand Gulf. (Contrary to popular belief, the Union army relied heavily on supplies from
Grand Gulf to sustain its movements in Mississippi. Only after reaching Vicksburg and
re-establishing contact with the fleet on the Yazoo River did Grant abandon the supply
line from Grand Gulf.) Instead of marching directly on Vicksburg from the south, Grant
marched his army in a northeasterly direction with his left flank protected by the Big
Black River.
It was Grant's intention to strike the Southern Railroad of Mississippi somewhere
between Vicksburg and Jackson. Destruction of the railroad would cut Pemberton's supply
and communications line and isolate Vicksburg. As the Federal force moved inland,
McClernand's Corps was on the left, Sherman's in the center, and McPherson's on the right.
