A soldier’s death is a reminder that more Americans have died fighting
the Taliban in 2019 than in any other year since 2014.
It’s difficult to answer your yes–no question directly because I’m not sure what you think being a “gerund” is supposed to mean in English, and because this is not a term that’s used much in modern English grammar.
So what I will instead do is explain these two things you need to know:
- What that word’s part of speech is: it’s a verb because it has a direct object argument.
- What its clause’s grammatical role is: it’s an adverbial because it’s modifying not complementing another verb.
Your original sentence is a complex declarative sentence containing not
just one main clause but also two subordinate ones. It also involves an
embedded than-comparison with an absent but recoverable verb of its very
own, but we won’t talk about that here.
Your sentence’s main clause necessarily uses a tensed finite verb, but only
one of your two subordinate clauses does so. The other subordinate clause
instead uses an untensed nonfinite verb, and it is this nonfinite
subordinate clause which you’ve asked about, the one containing an ‑ing verb.
As far as parts of speech go, the word fighting in your sentence is
neither a noun nor an adjective; it is clearly a verb. You can know this with
absolute certainty because fighting has a direct object, and having
direct objects is a property peculiar to verbs alone (and to active
transitive verbs in particular).
Fighting is the verb of the nonfinite clause fighting the Taliban and
other insurgent groups. Like many nonfinite clauses, this one has no grammatical subject. It does,
however, have a grammatical object, because its direct object is the
Taliban and other insurgent groups.
However, your question suggests that you want to know more than one word’s
part of speech taken in isolation. You appear to be interested in learning
the grammatical role which that entire phrase is fulfilling as a syntactic
Nonfinite clauses are able to serve in any grammatical role normally
fulfilled by substantives (like nouns and pronouns) or by modifiers (like
adjectives or adverbs). So now we need to figure out whether your entire
clause here is acting in ① a substantive role or ② in a modifier role.
The answer is that the second of those two possibilities applies. It’s
acting in a modifier role because one syntactic constituent is itself
modifying another syntactic constituent.
In particular, your fighting clause is acting as an adjunct to the other
subordinate clause, the one with the finite verb have died. Because your
clause is an adjunct to another clause, syntactically yours is a modifier.
Only if yours had been been a core argument to that other clause’s verb
(like by being its subject or direct object) would it have been used
in a substantive role. But it isn’t one of those. It’s only a modifier.
Modifiers of verbs are — by virtue of simple definition — always classified
as adverbial modifiers, never as adjectival modifiers. (Only in rare cases
can adverbs modify nouns, but this is a verb that’s being modified here, so
there’s no question of that anyway.)
So your fighting the Taliban clause is itself an adverbial phrase
that’s modifying the verb phrase have died. It’s limiting that verb
by saying how the Americans who died did so.
Once upon a time this clause would have been called an adverbial
participial phrase under outdated grammars of English. But modern English
grammars avoid words like gerund and participle, especially when trying
to describe a verb clause like yours. Often modern grammars prefer the
fused term gerund-participle for the verb’s ‑ing inflection in
nonfinite verb clauses like yours here.