He attained the rank of brigadier general was prominent during World War II for being relieved of his command of the 90th Infantry Division shortly after the Normandy landings.

[2][3][5] Following the 1891 death of his father, MacKelvie's mother moved her family to Illinois to live closer to their relatives.

[7] He later worked on construction of the Butte, Anaconda and Pacific Railway, a position he left in order to join the military.

[13] On July 1, 1940, while the United States was preparing for World War II, he was promoted to lieutenant colonel.

[14] He was promoted again, this time to the temporary rank of colonel, on December 11, 1941,[14] shortly after the United States entered World War II.

After service in the War Department's Plans Division at the start of World War II brought him to the attention of General George C. Marshall, the Army Chief of Staff, in March 1942 he was promoted to the temporary rank of brigadier general and named commander of the 85th Division Artillery.

Shortly after the invasion, the VII Corps commander, Major General Joseph Lawton Collins decided that the division was not performing satisfactorily in combat.

[25][26][27][28] MacKelvie was a member of the Calhoun County Board of Social Welfare, and was also involved in several civic projects, including the creation of the Hart–Dole–Inouye Federal Center and serving as vice president and president of the board of directors for the Battle Creek Civic Art Center.