There is the sentence:
In 1917, the United States entered the War assisting the Allies.
The problem is 'assisting the Allies.' What parts of speech are they? Are they a type of clause? Adjectival, adverbial?
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Sign up to join this communityIn 1917, the United States entered the War [assisting the Allies].
The bracketed element is a non-finite clause, more specifically a gerund-participial clause functioning as an adjunct (your adverbial) in clause structure.
Only words, not clauses, belong to a part of speech.