When the attack was made on
Fort Sumter, Schenck promptly tendered his services to the President. He later recalled his meeting with Lincoln: Schenck was commissioned
brigadier general of volunteers. Many West Point graduates sneered at political generals. Schenck had not been a military man, but he had been a diligent student of military science. On June 17, 1861,
Union Army Maj. Gen.
Irvin McDowell sent the
1st Ohio Volunteer Infantry Regiment (90–day) under the overall command of Schenck and the immediate command of Col.
Alexander McDowell McCook to expand the Union position in
Fairfax County, Virginia. Schenck took six companies over the
Alexandria, Loudon and Hampshire Railroad line, dropping off detachments to guard railroad bridges between
Alexandria, Virginia and
Vienna, Virginia. As the train approached Vienna, about north of
Fairfax Court House and from Alexandria, 271 officers and men remained with the train. On the same day,
Confederate States Army Col. Maxcy Gregg took the 6–month 1st South Carolina Infantry Regiment, about 575 men, two companies of cavalrymen (about 140 men) and a company of artillery with two artillery pieces (35 men), about 750 men in total, on a scouting mission from Fairfax Court House toward the Potomac River. On their return trip, at about 6:00 p.m., the Confederates heard the train whistle in the distance. Gregg moved his artillery pieces to a curve in the railroad line near Vienna and placed his men around the guns. Seeing this disposition, an elderly local Union sympathizer ran down the tracks to warn the approaching train of the hidden Confederate force. The Union officers mostly ignored his warning and the train continued down the track. The Union soldiers were riding open gondola or platform cars as the train backed down the track toward Vienna. The two forces were slightly out of effective musket range and few shots were taken by either side. As darkness fell, the Union force was able to retreat and to elude Confederate cavalry pursuers in the broken terrain. The Confederate pursuit also was apparently called off early due to apprehension that the Union force might be only the advance of a larger body of troops and because the Confederate force was supposed to return to their base that night. Confederates took such supplies and equipment as were left behind and burned a passenger car and five platform cars that had been left behind. The Union force suffered casualties of eight soldiers killed and four wounded. The
Battle of Vienna, Virginia followed the Union defeat at the
Battle of Big Bethel only a week earlier and historian William C. Davis noted that "the press were much agitated by the minor repulse at Vienna on June 17, and the people were beginning to ask when the Federals would gain some victories." Schenck's next appearance was at the
First Battle of Bull Run, July 21, 1861, where he commanded a brigade in Brig. Gen.
Daniel Tyler's division. After the tide of battle turned against the Union force and many units began to flee the battlefield, parts of Schenck's brigade, along with the
United States Regulars under
Maj. George Sykes, the brigade of three regiments of Germans under Col.
Louis Blenker, the brigade of Col.
Erasmus Keyes and the 1st and 2nd Rhode Island Infantry Regiments left the field in relatively good order as the remainder of the Union Army retreated in disorder. Schenck was subsequently in command under Maj. Gen.
William Rosecrans in West Virginia, and under Maj. Gen. John C. Fremont in the
Luray Valley. He took part in the
Jackson's Valley Campaign of 1862 in the
Shenandoah Valley, the
Battle of Cross Keys and was, for a time, commander of the
I Corps, in Maj. Gen.
Franz Sigel's absence. Ordered to join the
Army of Virginia, then under Maj. Gen.
John Pope, he joined it just before the
Second Battle of Bull Run, and was in the thick of the fighting of the two days that followed, being severely wounded on the second day, and his right arm permanently injured. He was promoted to major general September 18, 1862 to rank from August 30, 1862. Schenck was unfit for field duty for six months, but was assigned to the command of
VIII Corps, embracing the turbulent citizens of
Maryland, repressing all turbulence and acts of disloyalty or any complicity with treason. Schenck was not popular with the disloyal portion of the inhabitants of Maryland. In December 1863, he resigned his
commission to take his seat in Congress. ==Postbellum activities==