The United States are exposed to invasion through the whole extent of their Atlantic coast by any European power with whom we might be engaged in war--on the northern and northwestern frontier on the side of Canada by Great Britain, and on the southern by Spain or any power in alliance with her. If internal improvements are to be carried to the full extent to which they may be useful for military purposes, the power as it exists must apply to all the roads of the Union, there being no limitation to it. Wherever such improvements may facilitate the march of troops, the transportation of cannon, or otherwise aid the operations or mitigate the calamities of war along the coast or in any part of the interior they would be useful for military purposes, and might therefore be made. The power following as an incident to another power can be measured as to its extent by reference only to the obvious extent of the power to which it is incidental. So great a scope was, it is believed, never given to incidental power. If it had been intended that the right to declare war should include all the powers necessary to maintain war, it would follow that nothing would have been done to impair the right or to restrain Congress from the exercise of any power which the exigencies of war might require. The nature and extent of this exigency would mark the extent of the power granted, which should always be construed liberally, so as to be adequate to the end. A right to raise money by taxes, duties, excises, and by loan, to raise and support armies and a navy, to provide for calling forth, arming, disciplining, and governing the militia when in the service of the United States, establishing fortifications and governing the troops stationed in them independently of the State authorities, and to perform many other acts is indispensable to the maintenance of war--no war with any great power can be prosecuted with success without the command of the resources of the Union in all these respects. These powers, then, would of necessity and by common consent have fallen within the right to declare war had it been intended to convey by way of incident to that right the necessary powers to maintain war. But these powers have all been granted specifically with many others, in great detail, which experience had shown were necessary for the purposes of war. By specifically granting, then, these powers it is manifest that every power was thus granted which it was intended to grant for military purposes, and that it was also intended that no important power should be included in this grant by way of incident, however useful it might be for some of the purposes of the grant.