The situation demanded instant action, and in order that the import of Jackson’s movements may be fully realised it is necessary to turn to the main theatre of war.  McClellan, on April 5, with the 60,000 men already landed, had moved a few miles up the Peninsula.  Near the village of Yorktown, famous for the surrender of Lord Cornwallis and his army in 1782, he found the road blocked by a line of earthworks and numerous guns.  Magruder, Jackson’s captain in Mexico, was in command; but Johnston was still on the Rapidan, one hundred and thirty miles away, and the Confederates had no more than 15,000 men in position.  The flanks, however, were secured by the York and the James rivers, which here expand to wide estuaries, and the works were strong.  Yorktown proved almost as fatal to the invaders as to their English predecessors.  Before the historic lines their march was suddenly brought up.  McClellan, although his army increased in numbers every day, declined the swift process of a storm.  Personal reconnaissance convinced him that “instant assault would have been simple folly,” and he determined to besiege the intrenchments in due form.  On April 10 Johnston’s army began to arrive at Yorktown, and the lines, hitherto held by a slender garrison, were now manned by 53,000 men.

The Confederate position was by no means impregnable.  The river James to the south was held by the “Merrimac,” an improvised ironclad of novel design, which had already wrought terrible destruction amongst the wooden frigates of the Federals.  She was neutralised, however, by her Northern counterpart, the “Monitor,” and after an indecisive action she had remained inactive for nearly a month.  The York was less securely guarded.  The channel, nearly a mile wide, was barred only by the fire of two forts; and that at Gloucester Point, on the north bank, was open to assault from the land side.  Had McClellan disembarked a detachment and carried this work, which might easily have been done, the river would have been opened to his gunboats, and Johnston’s lines have become untenable.  He decided, however, notwithstanding that his army was more than 100,000 strong, that he had no men to spare for such an enterprise.

Magruder’s bold stand was of infinite service to the Confederate cause.  To both parties time was of the utmost value.  The Federals were still over seventy miles from Richmond; and there was always a possibility, if their advance were not rapidly pressed, that Johnston might move on Washington and cause the recall of the army to protect the capital.  The Confederates, on the other hand, had been surprised by the landing of McClellan’s army.  They had been long aware that the flotilla had sailed, but they had not discovered its destination; the detachments which first landed were supposed to be reinforcements for the garrison of the fortress; and when McClellan advanced on Yorktown, Johnston was far to the west of Richmond.  The delay had enabled him to reach the lines.* (* The first detachment of Federals embarked at Alexandria on March 16, and the army was thereafter transferred to the Peninsula by successive divisions.  On March 25 Johnston was ordered to be ready to move to Richmond.  On April 4 he was ordered to move at once.  On that date 50,000 Federals had landed.) But at the time Jackson fell back to Elk Run Valley, April 17 to 19, fortune seemed inclining to the Federals.