The primary reason Abraham Lincoln issued the Emancipation Proclamation was C. As a means to undermine the Southern war effort.
The proclamation, issued on January 1, 1863, declared the freedom of all enslaved people in Confederate-held territory. Lincoln aimed to weaken the Confederacy's ability to sustain its war effort by depriving it of laborers and to galvanize support for the Union cause, both domestically and internationally. While the proclamation had multiple implications, including influencing attitudes in Europe and setting the stage for future abolition efforts, its primary military strategy was to disrupt the Confederacy.