[2] He received two brevets for meritorious service during the Mexican–American War, to captain and major for the actions at Contreras, Churubusco, and Chapultepec.

In Mexico while serving under General Winfield Scott in the Army of Occupation, he received his nickname, "Fighting Dick",[note 1] which would carry over to the Civil War.

[4] 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.

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.

Large crowds lined the streets during his funeral procession to nearby Pontiac, where he was buried in Oak Hill Cemetery.

The Israel B. Richardson Camp #2 of the Sons of Union Veterans of the Civil War in Oakland, Michigan, was also named for the fallen general.