The Adumari Coalition was a confederacy of Adumari states opposed to Cartann, the largest Adumari nation-state, whose perator Pekaelic ke Teldan tried to forcefully form a world government with Cartann as its head. The first states which rejected his idea, were conservative governments of Halbegardia and Yedagon Confederacy, which itself was a group of nation-states with Yedagon as its main representative. Later Thozzelling and Tetanne and probably other small states joined this coalition.
The perator of Cartann, backed by Galactic Empire forces under General Turr Phennir, declared war on the rebelling Adumari states. General Wedge Antilles of the New Republic delegation, rejected his proposal of entry into the war. He and his companions (Wes Janson, Tycho Celchu, Derek Klivian) were therefore banished from Adumar, which meant they could be killed by anybody after leaving the perator's palace. Escalion, the perator of the Yedagon Confederacy, offered them sanctuary and asked Antilles to lead the Adumari Coalition forces against Cartann. He assured him that all leaders allied under anti-Cartann coalition banner had accepted his command.
The Yedagon Confederacy and its allies was victorious in the following Adumari Civil War. After taking control over Cartann City and the perator's palace by the coalition, Pekaelic ke Teldan abdicated at the instigation of Antilles, and his son Balass ke Teldan became the new perator of Cartann. The successor persuaded the victorious perators to grant amnesty to his state in order to form a strong and united government, which could stand against coming threat. Therefore the Adumari Union was established and Adumar joined the New Republic.
- X-Wing: Starfighters of Adumar (First appearance)