Idioms and Phrases with join forces
Act together, combine efforts. For example, The public relations people joined forces to get better coverage for their candidates. This expression originally referred to combining military forces. [Mid-1500s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.