It was soon after Burnside's unfortunate failure at Fredericksburg, perhaps the gloomiest period of the war, when military reverses saddened the whole North, and dissensions in the cabinet itself added to the embarrassments of the President, that Lincoln performed the most momentous act of his life, and probably the most important act of the whole war, in his final proclamation emancipating the slaves, and utilizing them in the Union service, as a military necessity. Ever since the beginning of hostilities had this act been urged upon the President by the antislavery men of the North,--a body growing more intense and larger in numbers as the war advanced. But Lincoln remained steady to his original purpose of _saving the Union,_---whether with or without slavery. Naturally, and always opposed to slavery, he did not believe that he had any right to indulge his private feeling in violation of the Constitutional limitations of his civil power, unless, as he said, "measures otherwise unconstitutional might become lawful by becoming indispensable to the preservation of the Constitution through the preservation of the nation." Thus when in 1861 Frémont in Missouri proclaimed emancipation to the slaves of persistent rebels, although this was hailed with delight by vast numbers at the North, the President countermanded it as not yet an indispensable necessity. In March, 1862, he approved Acts of Congress legalizing General B.F. Butler's shrewd device of declaring all slaves of rebels in arms as "contraband of war," and thus, when they came within the army lines, to be freed and used by the Northern armies. In March, May, and July, 1862, he made earnest appeals to the Border States to favor compensated emancipation, because he foresaw that military emancipation would become necessary before long. When Lee was in Maryland and Pennsylvania, he felt that the time had arrived, and awaited only some marked military success, so that the measure should seem a mightier blow to the rebels and not a cry for help. And this was a necessary condition, for, while hundreds of thousands of Democrats had joined the armies and had become Republicans for the war,--in fact, all the best generals and a large proportion of the soldiers of the North had been Democrats before the flag was fired on,--yet the Democratic politicians of the proslavery type were still alive and active throughout the North, doing all they could to discredit the national cause, and hinder the government; and Lincoln intuitively knew that this act must commend itself to the great mass of the Northern people, or it would be a colossal blunder.