The Battle of Grand Gulf was fought on April 29, 1863, during th: In early April, Bowen became aware of Grant's movement down the west side of the Mississippi River, and sent part of his force under the command of Francis Cockrell across the river on April 4, to counter the Union movement.[18]  Bowen informed Pemberton of Grant's advance, but the latter officer disregarded the information.[19]  The Union Navy forces cooperating with Grant, which were commanded by David Dixon Porter and known as the Mississippi Squadron, were positioned north of Vicksburg, but there was a need for vessels to move south for operations near Port Hudson, Louisiana,[20][21] as well as to provide a stronger protecting force for the transports that would ferry troops in Grant's planned crossing of the Mississippi River.[21]  Beginning two hours after nightfall on April 16, Porter ran several vessels past the batteries at Vicksburg, with the loss of only a transport and a barge.[22] Pemberton learned of the passing of the batteries, and began to develop a clearer picture of the true strategic situation.[23]  Grand Gulf was reinforced by Brigadier General Martin E. Green's brigade; when this unit arrived Pemberton elevated the concentration at Grand Gulf to divisional status with Bowen in command. With the addition of a miscellaneous command of 800 men and a four-gun battery sent from Jackson, Mississippi, there were about 4,200 Confederate troops around Grand Gulf.[24]