When the Civil War broke out, Richardson was still farming in
Michigan. He enlisted in the
Union Army and recruited and organized the
2nd Michigan Infantry. He married Fannie Travor on May 18, 1861, in
Wayne County, Michigan. When he reported with his
regiment in Washington, DC, General Winfield Scott greeted him with "I'm glad to have my 'Fighting Dick' with me again". Richardson, promoted to
colonel on May 25, 1861, was assigned command of the 4th Brigade, 1st Division, in the newly organized army of
Brigadier General Irvin McDowell. His brigade saw limited action at the
First Battle of Bull Run near
Blackburn's Ford, and in covering the subsequent federal withdrawal to Washington. He was promoted to brigadier general, ranking from May 17, 1861. He commanded several brigades in the
Army of the Potomac and then the 1st Division of the
II Corps during the
Peninsula Campaign in mid-1862. He was involved in the fighting at the battles of
Yorktown,
Seven Pines, and the
Seven Days. He was particularly distinguished in sharp fighting near the
Chickahominy River. Richardson was promoted to major general after the Seven Days Battles. His division was stationed in Washington, DC, during the
Second Battle of Bull Run and did not participate in that engagement. Richardson's 1st Division played a key role during the Battle of Antietam on September 17, 1862, attacking
Confederate positions in the center of the Sunken Road in support of the 3rd Division of Maj. Gen.
William H. French. After stubborn fighting, by 1:00 pm, Richardson had gained control of the high ground in front of the apex of the defensive line, and his men
enfiladed the remaining defenders in the road, which would gain the nickname "Bloody Lane" for the carnage. Richardson pushed forward beyond the road and was directing the fire of his artillery and organizing another attack when he was struck by a shell fragment. Carried to the rear, Richardson was treated at a
field hospital. His wound was not considered life-threatening, and he was given a room in Major General
George B. McClellan's headquarters, the Pry House. President
Abraham Lincoln paid his respects to the wounded Richardson during a visit to the battlefield in October. However, infection set in, and then
pneumonia, which claimed the life of the popular general in early November. He was among six generals to be killed or mortally wounded at Antietam. His body was escorted to Detroit. Large crowds lined the streets during his funeral procession to nearby Pontiac, where he was buried in Oak Hill Cemetery. ==Honors and awards==