foothold vs combat zone

foothold and combat zone both are nouns.

Word	Noun	Adjective	Verb	Adverb
foothold	Yes	No	No	No
combat zone	Yes	No	No	No

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

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

Other hypernyms of foothold include combat area.

foothold (noun)	combat zone (noun)
an initial accomplishment that opens the way for further developments	a military area where combat forces operate
a place providing support for the foot in standing or climbing	a city district known for its vice and high crime rate
an area in hostile territory that has been captured and is held awaiting further troops and supplies