His was a classic case of the politician-in-uniform coming into conflict with career Army officers, graduates of the United States Military Academy.

A friend and political ally of Abraham Lincoln, McClernand was given permission to muster a large force to conduct offensive operations against the confederate stronghold at Vicksburg, Mississippi, a campaign that would rival the effort of General Grant, his department commander.

Later on, McClernand's own expeditionary force departed southwards before his arrival, by design, commanded by General William T. Sherman, an ally of Grant.

Grant was later able to neutralize McClernand's independent effort after it conducted an expedition to capture the vital Fort Hindman on the Arkansas river, this unassuming victory had secured an important milestone in the future of the operations around the Mississippi river for months to come, and McClernand became the senior corps commander in Grant's army for the Vicksburg Campaign in 1863.

[1][13] The small coalition of Democratic representatives from Alabama and South Carolina opposing him objected to his moderate views on slavery and the importance of retaining the Union.

[16] He served as one of his campaign managers during the divisive Democratic presidential nomination convention held in Charleston, South Carolina in 1860.

[17] In November 1842, McClernand married Sarah Dunlap of Jacksonville, Illinois, a close friend of Mary Todd Lincoln.

[23] His commission as a general was based on Lincoln's desire to retain political connections with the Democrats of Southern Illinois, not on his brief service as a private in the Black Hawk War.

[24] At the same time, the brigade was placed in the District of Southeast Missouri commanded by Brigadier General Ulysses S. Grant, a subordinate of Fremont.

[25] In response to orders from Fremont on November 2 and 3, 1861, Grant sent regiments from his district in seven columns to demonstrate against Confederate forces on both sides of the Mississippi River.

[31] Near 8:00 a.m. on November 7, Grant's force began to disembark from transports about three and one-half miles (5.6 km) north of Belmont, out of range of Confederate artillery batteries across the river at Columbus, Kentucky.

[36] After his troops had disembarked from the gunboats, McClernand led his brigade toward the Confederate line formed in part by the recently arrived regiments of Gideon Pillow, about 3,000 men in total.

[43][45] After about one-half hour of unopposed disorder at the camp, the Confederate reinforcements along with reformed elements of Pillow's regiments routed the Union force, sending them retreating toward their gunboats, which provided covering fire.

[2][8][49][50] When reaching the shore, McClernand acted promptly to cover the boarding of the gunboats and to rescue a Union regiment which had been left behind.

[53] On the night of February 14, 1862, Confederate commanders decided to break out of the Union Army encirclement of the fort achieved the previous day.

[54] McClernand's division, whose flank was not sufficiently covered, was struck by a surprise attack in the early morning on February 15, 1862, the third day of the battle, in bitterly cold weather.

[65] On March 21, 1862, McClernand, who had boasted about and exaggerated the achievements of his division was promoted to major general of volunteers for his service at Fort Donelson.

[67] On April 5, 1862, McClernand responded to rumors and reports that the Confederates were preparing a surprise attack by sending out a cavalry party to scout but they did not go in the right direction or far enough in any event.

[68] In the early morning of April 6, 1862, the regiment of Brigadier General William T. Sherman's Fifth Division on the left flank, stationed about a quarter-mile south and east of Shiloh Church, began to give way under Confederate attack and the colonel's panic.

[75] Sherman's and McClernand's divisions were pushed back through the "Hornet's Nest", but held a firm line at Pittsburgh Landing as night fell.

[1][66][76] In October 1862, McClernand used his political influence with Illinois Governor Richard Yates to obtain a leave of absence to visit Washington, D.C. and President Lincoln, hoping to receive an important independent command.

Secretary of War Edwin Stanton agreed to order him north to raise troops for the expedition against Vicksburg which he would lead.

Grant obliged and wired McClernand in December 18 that preparations were finished and his corps was ready to proceed and "form part of the expedition against Vicksburg".

Early in January 1863, at Milliken's Bend, McClernand caught up with the expedition and assumed command from Sherman as the leader of the Union force that was to move down the Mississippi as part of the Vicksburg campaign.

[8] Sherman and acting Rear Admiral David D. Porter later convinced a disapproving Grant that leaving the Confederate garrison at Arkansas Post in place could have been an obstacle to the capture of Vicksburg.

[79] McClernand landed his men on the Mississippi River levee at Young's Point, where they "suffered from the heavy winter rains and lack of shelter.

Tents were not issued to the troops because they were within range of the [Confederate] guns at Vicksburg; so the more enterprising men dug holes in the levee and covered them with their black rubber blankets.

[81] The duty of notifying him of his dismissal fell to Lieutenant Colonel James H. Wilson, who'd held a grudge against him for an earlier chastising.

[83] President Lincoln, who saw the importance of conciliating a leader of the Illinois War Democrats, restored McClernand to a field command in 1864.

From April 27, 1864, through May 1, 1864, McClernand returned to the field to command the detachment of two divisions from the XIII Corps participating in the Red River Campaign.