Initially, Grant planned to cross his army from the west side of the river to the east at Grand Gulf, Mississippi, just below Vicksburg, where the Rebels had set up a pair of batteries that they styled "forts." City-class gunboats were among the vessels used to bombard the batteries on April 29, 1863. Although the fleet was able to silence the lower battery and reduce the rate of fire of the upper battery, they could not put the latter completely out of action. The operation was therefore considered to be a failure, and Grant had to revise his plans to cross farther downstream.