The cause of the Confederacy, although her white population of seven million souls was smaller by two-thirds than that of the North, was thus far from hopeless.  The North undoubtedly possessed immense resources.  But an efficient army, even when the supply of men and arms be unlimited, cannot be created in a few weeks, or even in a few months, least of all an army of invasion.  Undisciplined troops, if the enemy be ill-handled, may possibly stand their ground on the defensive, as did Jackson’s riflemen at New Orleans, or the colonials at Bunker’s Hill.  But fighting behind earthworks is a very different matter to making long marches, and executing complicated manoeuvres under heavy fire.  Without a trained staff and an efficient administration, an army is incapable of movement.  Even with a well-organised commissariat it is a most difficult business to keep a marching column supplied with food and forage; and the problem of transport, unless a railway or a river be available, taxes the ability of the most experienced leader.  A march of eighty or one hundred miles into an enemy’s country sounds a simple feat, but unless every detail has been most carefully thought out, it will not improbably be more disastrous than a lost battle.  A march of two or three hundred miles is a great military operation; a march of six hundred an enterprise of which there are few examples.  To handle an army in battle is much less difficult than to bring it on to the field in good condition; and the student of the Civil War may note with profit how exceedingly chary were the generals, during the first campaigns, of leaving their magazines.  It was not till their auxiliary services had gained experience that they dared to manoeuvre freely; and the reason lay not only in deficiencies of organisation, but in the nature of the country.  Even for a stationary force, standing on the defensive, unless immediately backed by a large town or a railway, the difficulties of bringing up supplies were enormous.  For an invading army, increasing day by day the distance from its base, they became almost insuperable.  In 1861, the population of the United States, spread over a territory as large as Europe, was less than that of England, and a great part of that territory was practically unexplored.  Even at the present day their seventy millions are but a handful in comparison with the size of their dominions, and their extraordinary material progress is not much more than a scratch on the surface of the continent.  In Europe Nature has long since receded before the works of man.  In America the struggle between them has but just begun; and except upon the Atlantic seaboard man is almost lost to sight in the vast spaces he has yet to conquer.  In many of the oldest States of the Union the cities seem set in clearings of the primeval forest.  The wild woodland encroaches on the suburbs, and within easy reach of the very capital are districts where the Indian hunter might still roam undisturbed.