At midnight on the third of May the Army of the Potomac crossed the Rapidan on five pontoon bridges, and marched at once into the Wilderness, where it remained during the whole of the fourth in order that its enormous train of 4,000 wagons and the reserve artillery of more than 100 guns might be protected in their passage across the river. It was Grant's hope to move by his left flank, out of the Wilderness, passing around his enemy, and placing himself with all his force between that enemy and the Confederate capital. But with that promptitude which was characteristic of all his operations, Lee anticipated this movement and struck at Grant's flank early on the morning of the fifth. The assault was made in the midst of the Wilderness--in a thicket so dense that it was impossible at many points for the men on one side to see those on the other, a hundred feet away. Every forward or backward movement involved a struggle through a tangle of vines and underbrush and young forest growths so thickly standing as to render all progress difficult, and all regularity of formation impossible. On either side no corps or regiment or company could know what its own friends were doing on its right or its left; no officer could tell whether he was being supported on his flank or had been abandoned there; no steadiness or cohesion was possible. No alignment could be maintained. It is doubtful to-day that any officer on either side in that struggle, from Grant and Lee at the top to the smallest commander at the other end of the line, ever had a clear-cut idea of the course that that day's fighting took. It consisted of a series of irregular assaults made with desperate valor, and repelled with equal determination. It resembled nothing so much as a battle in the dark, the one thing which all commanders most dread, and most sedulously avoid. Very naturally the fighting was at short range at every point. Scarcely anywhere on that tangled field did the opposing forces discover each other's positions until they came within short pistol-shot range. The slaughter was therefore tremendous and at no time could either commanding general fully satisfy himself as to how the battle was going or what its result was likely to be or even what his own or the enemy's position was. The two greatest fighting machines that America has yet produced had met in battle, in the midst of such a maze of tangled growths as nowhere else exists except in marshes where such a meeting is impossible by reason of a lack of firm ground for the men to stand upon. Here at least, there was firm ground.