On March 11, 1858, he was commissioned aide-de-camp to the major general commanding the 3rd Division of the uniformed militia of Chester and Delaware counties.

[1] In the spring of 1861, Bell promptly responded to President Abraham Lincoln's call for volunteers to suppress the Southern secessionists.

On November 18, 1861, the regiment left Camp Curtin and traveled to Annapolis, Maryland, where they drilled for six weeks before embarking for military operations on the coast of North Carolina on January 6, 1862.

[1][3] Burnside's North Carolina Expedition was a Union naval and infantry assault aimed at closing blockade-running ports inside the Outer Banks.

Also at New Bern, he commanded a detachment that dragged army's artillery through downpours along muddy roads in time for the Union attack, for which he earned personal thanks from General Ambrose Burnside.

[1][3][4] During this period, Bell was nominated for colonel of the newly formed 124th Pennsylvania Infantry Regiment (composed largely of Chester County volunteers).

Soon after the Union troops seized the bridge, grapeshot struck Bell in the left temple and inflicted a mortal wound.