Serving under Maj. Gen. Gordon Granger, the 77th Illinois Volunteers participated in the bloody initial phase of the Vicksburg Campaign, during which several days of futile Union attacks were launched before a protracted siege was made and won.

[3] After participating in the first Vicksburg battles, the 77th was part of the group of Union troops marched to the east, where on May 14, 1863, they took part in the Battle of Jackson, Mississippi, leading to the fall of that city.

In April 1864, having marched into Louisiana towards Alexandria, the unit was isolated and crushed in a cavalry support operation at the Battle of Sabine Cross-roads.

[3] Some 176 officers and men of the 77th Illinois were killed, wounded, or captured, leaving only 125 members of the regiment fit for duty.

[3] The regiment suffered 2 officers and 66 enlisted men who were killed in action or mortally wounded and 1 officer and 137 enlisted men who died of disease, for a total of 206 fatalities.