[6] His classmates at the U.S. Military included several men who would also eventually attained the rank of brigadier general or higher in their military careers, including James B. Aleshire, Charles Justin Bailey, John Loomis Chamberlain, James Brailsford Erwin, George Washington Goethals, Henry Granville Sharpe, Frederick S. Strong, and others.

In 1907, Bell was appointed to the Infantry Equipment Board, taking part in the design of many items that were later used in World War I.

[3][11] Shortly after the American entry into World War I in April 1917, Bell was promoted to major general and assigned to command the Illinois National Guard's 33rd Division.

He commanded throughout the war, with the 33rd, after months of strenuous training in the United States and arriving on the Western Front in May 1918, attaining distinction as the only American division to fight under its own flag and as part of British Empire (Australian) and French corps.

After the war he commanded the Sixth Corps Area, with headquarters in Chicago, Illinois, until reaching the mandatory retirement in 1923 at age 64.