firepower vs military strength

firepower and military strength both are nouns.

Word	Noun	Adjective	Verb	Adverb
firepower	Yes	No	No	No
military strength	Yes	No	No	No

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

firepower: (military) the relative capacity for delivering fire on a target
military strength: capability in terms of personnel and materiel that affect the capacity to fight a war

Other hypernyms of firepower include military capability, military posture, posture, strength.

firepower (noun)	military strength (noun)
(military) the relative capacity for delivering fire on a target	capability in terms of personnel and materiel that affect the capacity to fight a war