GHQ vs military headquarters

GHQ and military headquarters both are nouns.

Word	Noun	Adjective	Verb	Adverb
GHQ	Yes	No	No	No
military headquarters	Yes	No	No	No

As nouns, military headquarters is a hypernym of GHQ; that is, military headquarters is a word with a broader meaning than GHQ:

GHQ: military headquarters from which a military commander controls and organizes the forces
military headquarters: the military installation from which a commander performs the functions of command

Other hypernyms of GHQ include headquarters, HQ.

GHQ (noun)	military headquarters (noun)
military headquarters from which a military commander controls and organizes the forces	the military installation from which a commander performs the functions of command