John G. Nicolay, A Short Life of Abraham Lincoln, condensed from Nicolay and Hayes' Abraham Lincoln: A History

According to geographical features, the second great field of strategy lay between the Alleghany Mountains and the Mississippi River, and the third between the Mississippi River, the Rocky Mountains, and the Rio Grande. Except in Western Virginia, the attitude of neutrality assumed by Kentucky for a considerable time delayed the definition of the military frontier and the beginning of active hostilities in the second field, thus giving greater momentary importance to conditions existing and events transpiring in Missouri, with the city of St. Louis as the principal center of the third great military field.

The same necessity which dictated the promotion of General McClellan at one bound from captain to major-general compelled a similar phenomenal promotion, not alone of officers of the regular army, but also of eminent civilians to high command and military responsibility in the immense volunteer force authorized by Congress. Events, rather than original purpose, had brought McClellan into prominence and ranking duty; but now, by design, the President gave John C. Fremont a commission of major-general, and placed him in command of the third great military field, with headquarters at St. Louis, with the leading idea that he should organize the military strength of the Northwest, first, to hold Missouri to the Union, and, second, by a carefully prepared military expedition open the Mississippi River. By so doing, he would sever the Confederate States, reclaim or conquer the region lying west of the great stream, and thus reduce by more than one half the territorial area of the insurrection. Though he had been an army lieutenant, he had no experience in active war; yet the talent and energy