From Longman Dictionary of Contemporary Englishjoin battlejoin battleformalFIGHT to begin fighting → join
Examples from the Corpus
join battle• He could have joined battle, lost, and opted for some face-saving rapprochement.• It would certainly distract the attention of the powerful commercial groups that are about to join battle over cable television networks.• A nationalist militia, the Mai Mai, has also joined battle with both sides. 