General McDowell's "invasion of Virginia" on May 23 was followed by several weeks of military inactivity on the Potomac, broken only by a dash of the Union cavalry into Fairfax Courthouse and the skirmish at Vienna, where a regiment of Ohio troops, who were backed on a railroad train into a rebel ambuscade, lost twenty men. On July 16 the Union army began a forward movement against the rebels who were found in position about and along a creek known as Bull Run. After a short and indecisive engagement on that day, General McDowell commenced to concentrate his forces for an attack on Beauregard's line, but various delays prevented any definite movement until Sunday, July 21. On that date was fought the battle of Bull Run, ending in a complete Union defeat, attended by severe losses and a panic-stricken retreat by many regiments, and followed by great national dismay and alarm. An inquiry into the blundering strategy, political half-heartedness, and poor generalship, which were the causes of this unnecessary and most serious reverse, are foreign to the purpose of this work. Mr. Chandler was one of a large number of members of Congress who joined the army on the eve of battle, and watched its progress to the final disaster. The First Michigan was among the regiments engaged in the thickest of the fight, and the Second and Third were in the brigade of Gen. I. B. Richardson, which acted as a rear-guard in the retreat of the army and prevented defeat from becoming a total rout. Mr. Chandler himself aided in halting and rallying the panic-stricken fugitives,[21] and reached Washington late at night, covered with mud and wearied with travel and hunger. He drove at once to the White House, where he found Mr. Lincoln despondent, exhausted with his labors, and greatly depressed by the defeat and the loss of life involved. Mr. Chandler urged upon the President the necessity of vigorous measures, the wisdom of calling for more troops, and the certainty that the North would follow the Administration in meeting a reverse with undismayed and redoubled energies. He asked Mr. Lincoln to issue an order for the enrolling of 500,000 men at once, "to show to the country and the rebels that the government was not discouraged a whit, but was just beginning to get mad." Mr. Chandler's vitality, the timely vigor of his bold words, and his overwhelming earnestness acted as a tonic upon the over-burdened Executive, and he left Mr. Lincoln cheered, encouraged and resolute. The governors of the loyal States were at once appealed to for more troops, and the answer of the North to Bull Run was the rush of tens of thousands of men into camp and the organization of great armies along the Potomac, the Ohio and the Mississippi. Secretary Stanton, who knew of this midnight interview, estimated its effect upon the course of events as of the utmost importance, and repeatedly said that Mr. Chandler's opportunely-manifested courage and vigor then saved the Union from a great peril.