Union General Winfield Scott, who was commander-in-chief of the armies of the United States at the beginning of the war, was old and infirm, and he soon retired. Union General George B. McClellan, by his well-planned battle at Rich Mountain, in western Virginia, shown capacity, and he was now called to command the forces in front of Washington. He spent eight months in organizing and disciplining his army.

Instead of moving directly against the Confederate forces lying in front of him, McClellan thought best to take his army by water to Fortress Monroe, and from there to go up between York River and James River toward Richmond. The land between these two rivers forms a peninsula; this is therefore known as the Peninsular campaign. From the beginning, the campaign was unfortunate in many ways. Part of the troops which McClellan expected to receive were detained for the defense of Washington. The Confederates forced him to spend a month in the siege of Yorktown. Yorktown was evacuated on the 5th of May. McClellan's troops pursued the retiring Confederates, and fought the Battle of Williamsburg that day. The Confederates retreated at night toward Richmond.

But the Confederate general, Thomas J. Jackson, who had got the nickname of "Stonewall" Jackson in the first Battle of Bull Run, and who was operating in the Valley of Virginia, now made a series of rapid maneuvers, by which he defeated or confused several bodies of Union troops and frightened the authorities at Washington, so that Union General Irvin McDowell's troops at Fredericksburg were held back from joining McClellan before Richmond. Meantime the Confederate army defending Richmond, under General Joseph E. Johnston, fought the Battle of Fair Oaks, by attacking one wing of McClellan's army while it was divided into two parts by the Chickahominy River, and won a partial success. Johnston having been wounded in this battle, General Robert E. Lee succeeded him. Stonewall Jackson now slipped away from the Valley of Virginia, and suddenly brought his army down by rail to assist Lee in the struggle against McClellan.

McClellan withdrew his forces to the James River. About this time the two armies were engaged every day; these conflicts are known as the Seven Days' battles. For a whole week the Confederates beat upon McClellan's army. Its months of discipline and drill enabled it to fall back slowly before Lee's furious onslaught.

But McClellan's first plan had failed. The President had lost confidence in McClellan's ability to overmatch such generals as Lee and Stonewall Jackson. A new general must be found. Pope, whose energy and success at Island No. 10 had given him reputation, was put in command of the army in front of Washington, and the army on the James River was brought back by degrees to reinforce him.

But Pope proved not to be equal to the generals in his front. Stonewall Jackson made a great circuit around through Thoroughfare Gap, and cut off Pope's communications with Washington. The Federal army fought bravely on the old Bull Run battlefield (August 29 and 30, 1862), and Pope showed his usual energy, but his enemy had beaten him in skillful maneuvers, and his army fell back disheartened to the neighborhood of Washington again, where it was a year before.

McClellan, who, in spite of the unfortunate outcome of his Campaign, had won the confidence of the soldiers in the Eastern army, was now again put in command of it. Lee followed up his advantages by crossing the Potomac. Meantime he sent a force and captured Harper's Ferry, with eleven thousand Union soldiers. On the 16th and 17th of September McClellan and Lee fought one of the severest battles of the war at Antietam Creek, near Sharpsburg, in Maryland. On the 18th Lee withdrew across the Potomac, and McClellan followed slowly, and again made the Rappahannock his line.

But McClellan had lost the confidence of his superiors, and he was now finally removed. General Burnside was next put in command of this unlucky army. McClellan had been thought too cautious, but Burnside was rash. He crossed the Rappahannock at Fredericksburg, and assailed the Confederate works on the heights back of the town on December 13, 1862. His army was defeated with great slaughter.

Burnside was relieved, and General Hooker was tried. In the spring of 1863 General Hooker fought what was called the Chancellorsville campaign, where, like those who had gone before him, he was outmaneuvered by Lee's generalship and Stonewall Jackson's marching qualities. On May 6th Hooker re-crossed the Rappahannock.

Lee soon after crossed the Potomac, and pushed his veteran army into Pennsylvania, striking for Harrisburg. Hooker was relieved from commanding the army opposed to Lee, and General George G. Meade succeeded him. Near Gettysburg, in Pennsylvania, the vanguards of the two great armies met on the 1st day of July, 1863, The people of the North and those of the South were filled with fear and anxiety as this battle approached. The courage of the troops on both sides was simply marvelous. On the second day of the battle the Confederates carried works at both ends of the Union line. The next day the Union army recovered the lost ground on its right. The Confederates then made a tremendous assault and broke through the center of the Federal army, but they were soon driven back defeated. Lee's army rested a day and then retreated, Lee had lost about one third of his soldiers; Meade had lost a good deal more than a fourth of his. In all, about forty-eight thousand had been killed, wounded, or captured in this awful struggle between two veteran and resolute armies.