There is a simple but very fruitful remark of a Swiss military writer, that every military line may be conceived as having three parts, the middle and the two ends, or flanks. As sound principle requires that military effort should not be distributed along the whole of an enemy’s position,—unless in the unusual case of overwhelming superiority,—but that distinctly superior numbers should be concentrated upon a limited portion of it, this idea of a threefold division aids materially in considering any given situation. One third, or two thirds, of an enemy’s line may be assailed, but very seldom the whole; and everything may depend upon the choice made for attack. Now the British frontier, which the United States was to assail, extended from Montreal on the east to Detroit on the west. Its three parts were: Montreal and the St. Lawrence on the east, or left flank; Ontario in the middle, centering at Kingston; and Erie on the right; the strength of the British position in the last-named section being at Detroit and Malden, because they commanded the straits upon which the Indian tribes depended for access to the east. Over against the British positions named lay those of the United States. Given in the same order, these were: Lake Champlain, and the shores of Ontario and of Erie, centering respectively in the naval stations at Sackett’s Harbor and Presque Isle. Accepting these definitions, which are too obvious to admit of dispute, what considerations should have dictated to the United States the direction of attack; the one, or two, parts out of the three, on which effort should be concentrated? The reply, as a matter of abstract, accepted, military principle, is certain. Unless very urgent reasons to the contrary exist, strike at one end rather than at the middle, because both ends can come up to help the middle against you quicker than one end can get to help the other; and, as between the two ends, strike at the one upon which the enemy most depends for reinforcements and supplies to maintain his strength. Sometimes this decision presents difficulties. Before Waterloo, Wellington had his own army as a center of interest; on his right flank the sea, whence came supplies and reinforcements from England; on his left the Prussian army, support by which was imminently necessary. On which flank would Napoleon throw the weight of his attack? Wellington reasoned, perhaps through national bias, intensified by years of official dependence upon sea support, that the blow would fall upon his right, and he strengthened it with a body of men sorely needed when the enemy came upon his left, in overwhelming numbers, seeking to separate him from the Prussians.