The Coalition was formed after Arf Fey'lya rallied his allies in the Democratic Republican Party and in the rest of the galaxy to break the Republic's siege of Ossus after a disagreement between Mezzileen and the Jedi. After the siege was broken, Jedi Grand Master Yoda was persuaded to lead the Jedi in a coalition against Mezzileen and the Republic. Afterwards the Coalition regrouped and engaged in the Mezzilenic War with the Republic.