NO threat to the continued existence of a nation and its government is so exacting, no species of political and social upheaval is so ominous, as the crisis of civil war. The attempt of a large and discontented segment of the population to seize power or win independence by force of arms is as potent a, menace to constitutional government as can well be imagined. Thus it is that the War of 18611865, certainly one of the most bitter and bloody civil struggles in all recorded history, was the most dangerous emergency ever faced by a government of the United States. The four years of the Civil War remain even today the most critical in the life of the Republic. The principle and the institutions of constitutional dictatorship played a decisive role in the North's successful effort to maintain the Union by force of arms.