From Longman Dictionary of Contemporary Englishjoin up with somebody/something phrasal verbWITHto combine with or meet other people in order to do something Three months ago, they joined up with another big company that sells arms. → join→ See Verb table
Examples from the Corpus
join up with • Before diving offshore, get local knowledge or join up with a club who has dived the site previously.• That's likely to join up with a new A-road to East Anglia.• And three months ago, he joined up with another big outfit that sells arms.• She was also mustering troops, and planned to lead them northwards to join up with her son.• I have to join up with my friends.• What do you suppose might happen if the soccer moms join up with Norma Rae?• Mattie has joined up with the outsiders. 