in the 1960s, kalergis served tours in south korea and as commander of 2nd armored division (united states) at fort hood, texas. during the vietnam war from 1967 to 1968, he commanded the artillery for the corps-level organization i field force, vietnam (united states). the next year, he served as first field force's chief of staff. in vietnam, he was recognized in efforts to quantify and reduce "harassment and interdiction fire", artillery fire intended to reduce enemy morale and movement. 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.