When squads or scouting parties meet each other, they either fight in an irregular fashion or they run away. With a systematic battle it is different. Before a systematic battle, one army selects some place at which to resist the advance of the other. The advancing army usually cannot leave the other aside and go on by another route to the capital city which it wants to reach, because, if it did, the army left aside would quickly destroy what is called the advancing army’s “communications.” To destroy these communications would be to cut off supplies of food, ammunition, and everything else necessary to an army. The army which takes the defensive selects some point that can be most easily defended,—some point where a river or a creek, or a line of hills, or something else, serves to give it the advantage in a fight. The enemy must either attack that army there, and drive it out of its position, or it must “flank” it out, if it is itself to go forward. To “flank” an army out of position is not merely to pass it by, which, as explained above, might be dangerous, but to seize upon some point or some road, the possession of which will compel that army to retire. Thus, when General Lee could not be driven out of his works at Fredericksburg by direct attack, General Hooker marched his army up the river, and by crossing there placed himself nearer Richmond than General Lee was. This compelled General Lee to abandon his position at Fredericksburg, and to meet General Hooker in the open field; otherwise there would have been nothing to prevent General Hooker from going to Richmond, with a part of his greatly superior force, leaving the rest of it to check any operations Lee might have undertaken against his communications. It is in some such fashion as this that every battle is brought about. One side is ever trying to get somewhere, and the other side is ever trying to prevent it from doing so. Incidentally, each army is trying to destroy the other.