I went to the Peninsula as soon as possible, reaching General Magruders headquarters early in the morning; and passed the day examining his works with the assistance of General Whiting, who accompanied me for that purpose, and in obtaining all the pertinent information General Magruder could give.
That officer had estimated the importance of at least delaying the invaders until an army capable of coping with them could be formed; and opposed them with about a tenth of their number, on a line of which Yorktown, in trenched, made the left flank. This boldness imposed upon the Federal general, and made him halt to besiege instead of assailing the Confederate position. This resolute and judicious course on the part of General Magruder was of incaluable value. It saved Richmond, and gave the Confederate Government time to swell that officer's handful to an army.

This is from "NARRATIVE OF MILITARY OPERATIONS DURING THE CIVIL WAR" by Joseph E. Johnston.