Vicksburg was the last major Confederate stronghold on the Mississippi River; therefore, capturing it completed the second part of the Northern strategy, the Anaconda Plan.
When two major assaults (May 19 and 22, 1863) against the Confederate
fortifications were repulsed with heavy casualties, Grant decided to
besiege the city beginning on May 25. With no reinforcement, supplies
nearly gone, and after holding out for more than forty days, the
garrison finally surrendered on July 4.
