One of the two armed factions that carved up the failed colony of Turkana IV, led by Hayne, which used Tasha Yar's sister Ishara to manipulate the Enterprise crew.
The Coalition is one of the cadres that took control of Turkana IV after its government collapsed. The factions had first been given police powers to keep order, but ended up fighting each other for territory in the colony's underground tunnels, each member fitted with an implant that set off alarms in enemy territory.
In the Next Generation episode Legacy the Enterprise-D comes to rescue the crew of the freighter Arcos, who are being held by the rival Alliance. The Coalition's leader Hayne offers help and assigns Ishara Yar, sister of the late Tasha Yar, as liaison.
Ishara wins Data's trust, has her implant removed and joins the rescue team, but her real mission is to shut down the Alliance's defences so the Coalition can attack. Data and Riker stop her.