military man vs serviceman

military man and serviceman both are nouns.

Word	Noun	Adjective	Verb	Adverb
military man	Yes	No	No	No
serviceman	Yes	No	No	No

As nouns, military man and serviceman are synonyms defined as:

military man and serviceman: someone who serves in the armed forces; a member of a military force

Other synonyms of military man include man, military personnel.

military man (noun)	serviceman (noun)
someone who serves in the armed forces; a member of a military force	someone who serves in the armed forces; a member of a military force