Lincoln was counting on a brief war with the South as he raised an army – without Congressional approval – to send southward. The army of General McDowell was full of 90-day volunteers and battle had to be joined (and won) before they went home with the government’s $100 in their pockets. The battle of First Manassas was a Northern debacle which cooled the alleged flag-insult at Fort Sumter and it became obvious to Lincoln’s War Department that generous enlistment bounties were necessary to keep men in blue uniforms. Between 1861-1865 the North paid about $750,000,000 in bounties to fill its ranks. An excellent resource is William Marvel’s “Lincoln’s Mercenaries,” LSU Press, 2018.
Penalty for Not Re-Enlisting
Author Jonathan W. White’s book “Emancipation, the Union Army and the Reelection of Abraham Lincoln” (LSU Press, 2014) suggests that Secretary of War Edwin Stanton utilized intimidation tactics to ensure Lincoln’s election and use the soldier vote to help accomplish it. His assistant secretary, Charles A. Dana, admitted to using the full power of the War Department to ensure Lincoln’s electoral triumph. Stanton was also creative in his filling the ranks with blue soldiers as the unpopular war wore on.
By May 1864, the initial three-year enlistments had expired and strong measures utilized for re-enlisting the veterans. The hated draft was causing riots in northern cities, and Grant complained often of the useless soldiers he was sent — paid substitutes and draftees who often deserted at the first opportunity.
Desperate to retain the veterans, Stanton demanded additional government bounty money to entice them to stay, one-month furloughs home to show off their “Veteran Volunteer” sleeve chevrons, and commanders rewarded with promotions for re-enlistments obtained. Commanders unsuccessful in their re-enlistment efforts were denied promotion or cashiered.
The bounty money made soldiers wealthy men for the time, but naturally caused them to avoid battle in order to spend it. White estimates that only 15 percent of veteran soldiers re-enlisted, leaving 85 percent who walked away, as it had become an abolition war rather than the “save the Union” banner they had enlisted under. Additionally, they saw emancipation bringing many black freedmen north in search of employment, thus depressing wages and taking jobs from white northerners.
“In May  the three-years’ service of the regiment had expired; and three hundred and seventy-five men who had not reenlisted as veterans were mustered out and made their way home as best they could. On arriving in New York, they drew up and adopted a series of resolutions. They began by rehearsing an order of Col. [Henry L.] Abbot, dated May 21, urging them to “stand by their colors, and not march to the rear to the sound of the enemy’s cannon.”
The reason for their non-re-enlistment seems to be stated in the charge against Col. Abbot:
“That he has spared no pains to place over us a military aristocracy, subjecting us to every variety of petty annoyance, to show his own power, and take away our manhood; subjecting men to inhuman and illegal punishments for appealing to him for justice; disgracing others for attempting to obtain commissions in colored regiments; . . . about May 4 ordering his heavy artillery men who had not re-enlisted, into the ditch for the remainder of their term of service, thus placing us on a level with prisoners under sentence for court-martial; and finally capping the climax by leaving us to the tender mercy of provost-marshals, turning us loose on the world, without pay, without officers, without transportation, without rations and without our colors.”
(The Military & Civil History of Connecticut, During the War of 1861-1865. W. Croffut & J. Morris. Ledyard Bill. 1869, pg. 558-559)