彼らは力を合わせて敵と戦った。

they (usually male); them

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

force; strength; might; vigour (vigor); energy; capability; ability; proficiency; capacity; faculty; efficacy; effect; effort; endeavours (endeavors); exertions; power; authority; influence; good offices; agency; support; help; aid; assistance; stress; emphasis; means; resources

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to match (rhythm, speed, etc.); to join together; to unite; to combine; to add up; to face; to be opposite (someone); to compare; to check with; to cause to meet (e.g. an unpleasant fate); to place together; to connect; to overlap; to mix; to combine; to put blade to blade; to fight

opponent; rival; adversary; menace; danger; threat; enemy

if; when; and; with; particle used for quoting (with speech, thoughts, etc.); quoting particle; promoted pawn; indicates question (sentence end)

to make war (on); to wage war (against); to go to war (with); to fight (with); to do battle (against); to compete (against); to struggle (against adversities, etc.); to fight; to contend; to resist