bridgehead vs combat area

bridgehead and combat area both are nouns.

Word	Noun	Adjective	Verb	Adverb
bridgehead	Yes	No	No	No
combat area	Yes	No	No	No

As nouns, combat area is a hypernym of bridgehead; that is, combat area is a word with a broader meaning than bridgehead:

bridgehead: an area in hostile territory that has been captured and is held awaiting further troops and supplies
combat area: a military area where combat forces operate

Other hypernyms of bridgehead include combat zone.

bridgehead (noun)	combat area (noun)
an area in hostile territory that has been captured and is held awaiting further troops and supplies	a military area where combat forces operate
a defensive post at the end of a bridge nearest to the enemy