After his successes at Jackson, Champion Hill and Big Black River, Grant assumed that Confederate morale might be low enough that Vicksburg could be taken by assault and avoid a time consuming siege. In that he was mistaken. The Confederates lacked the strength to defeat him in open battle. but they had both the strength, and the morale, to hold Vicksburg. The first assault by Grant occurred on May 19, 1863 and was aimed at the Stockade Redan.