Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mīlĭtārĭus, a, um, adj. [miles], soldierlike, military (ante-class.): gradus, Plaut. Ps. 4, 4, 11.
Hence, adv.: mīlĭtārĭē, in a soldier-like or military manner (postclass.): militarie caesus, Treb. Trig. Tyrann. 22 dub.