His career spanned the World War II and post-Vietnam eras, and he played a significant role in the post-Vietnam-era reorganization of the Army.
His education continued during his military career when he earned a master's degree in international relations at George Washington University and attended the six-week Advanced Management Program at Harvard Business School.
By November 1943, he was a captain and battalion adjutant and promoted to major shortly after the unit arrived in France in February 1945.
Yet in practice, it was rarely observed or checked for results and generally proved useless in countering enemy activities in a war without fronts.
Kalergis developed systems to quantify and significantly reduce its use due to ineffectiveness, collateral damage to civilians and its high cost.
In 1974 Kalergis succeeded Glenn D. Walker as commanding general of the First United States Army at Fort Meade, Maryland.
[11] After retiring from the military, in 1976 Kalerigis chaired a task force that drafted an action plan Tank Weapon System Management.