From Longman Dictionary of Contemporary Englishjoin/combine forces (with somebody/something)join/combine forces (with somebody/something)UNITEto work together so that you can deal with a problem, be more powerful etcjoin forces to do something Local schools have joined forces with each other to share facilities. → force
Examples from the Corpus
join forces to do something• The state environmental bodies and the militia are joining forces to set up mobile anti-poaching units.• Now parents, governors and staff are joining forces to call for seat belts on coaches.• Tim Roemer, D-Ind., was voted down 289-121, with Republicans and Democrats joining forces to defeat it.• They emerge from the apparatus of inheritance, from the ways that genes join forces to do their job.• Two London gangs had joined forces to stop the train at Sear's Crossing in Buckinghamshire by rigging the signals.• Police in Cheshire and Greater Manchester have joined forces to investigate a series of attacks which span more than six years.• So shopkeepers have joined forces to attract people into the town, with a special publication circulated in neighbouring areas.• Read in studio Cancer specialists have joined forces to improve the treatment of sick children. 