The Republican defeat of the Crittenden Compromise and subsequent thirteenth amendment to the Constitution, which Lincoln endorsed, opened the path to war prosecuted by the North. Lincoln let it be known to Republicans that no compromise or peaceful settlement of issues dividing the country would be tolerated before his inauguration, as he put his party above the safety and continuance of the Founders’ Union.
Bernhard Thuersam, www.Circa1865.org
“On Whom Rests the Blame for the Civil War”
“From Buffalo, on January 18, 1861, [Horatio Seymour] wrote Senator [John J.] Crittenden of Kentucky in support of his scheme of compromise. It was in his opinion that this “great measure of reconciliation” struck “the popular heart.” James Ford Rhodes fortified one’s belief in the good judgment of Seymour when he studied the defeat of Senator Crittenden’s proposals. In view of the appalling consequences the responsibility of both Lincoln and [William] Seward for that defeat is heavy, if not dark – in spite of all that historians of the inevitable have written of “this best of all possible worlds.”
The committee to which Crittenden’s bill for compromise was referred consisted of thirteen men. Crittenden himself was the most prominent of the three representatives from the Border States. Of three Northern Democrats, [Stephen] Douglas of Illinois, was the leader; of five Republicans, Seward was the moving spirit. Only two men sat from the Cotton States, [Jefferson] Davis and [Robert] Toombs. Commenting on the fateful vote of the committee, Rhodes observed:
“No fact is more clear than that the Republicans in December  defeated the Crittenden compromise; a few historic probabilities have better evidence to support them than the one which asserts that the adoption of this measure would have prevented the secession of the cotton States, other than South Carolina, and the beginning of the civil war in 1861 . . . It is unquestionable, as I have previously shown, that in December the Republicans defeated the Crittenden proposition; and it seems to me likewise clear that, of all the influences tending to this result, the influence of Lincoln was the most potent.”
Two-thirds of each House . . . recommended to the States a compromise thirteenth amendment to the Constitution, as follows: “No amendment shall be made to the Constitution which will authorize or give to Congress the power to abolish or interfere, within any State, with the domestic institutions thereof, including that of persons held to labor or service by the laws of said State.” Conservative Republicans voted with the Democrats to carry this measure of which Lincoln approved in his inaugural address.
“As bearing on the question on whom rests the blame for the Civil War,” observes Rhodes, this proposed thirteenth amendment and its fate is of the “highest importance.”
(Horatio Seymour of New York, Stewart Mitchell, Harvard University Press, 1938, pp. 223-224)