The Battle of the Ceres Ocean, also known as Operation Glory Horn or Sea of Chaos is one of the last missions of Ace Combat 5: The Unsung War and the Circum-Pacific War. This is the last appearance of the Osean 3rd Naval Fleet's "invincible" carrier Kestrel. The battle was fought between the Kestrel Fleet and multiple defecting Yuke ships, against a Nationalist Yuktobanian Fleet. A Nationalist Osean Fleet later joins the fray. The location of the battle was the middle of the Ceres Ocean.
On December 29, 2010, a fleet of Yuktobanian Maritime Force ships sailed toward the Kestrel Fleet. Captain Nicholas A. Anderson and Yuktobanian Prime Minister Nikanor, who was on board the Kestrel, called out to the Yuktobanian Fleet. The Prime Minister announced that he was on the Osean aircraft carrier Kestrel and that he planned to restore peace between "Our Yuktobania, and the country of Osea". However, the Yuktobanian Fleet Commander denied peace between the two countries and decided to sink the carrier with the Yuktobanian Prime Minister on board, saying that he had sided with the Oseans. But the captain of the Krivak class frigate ship Pitomnik disagreed and wanted to defend the Prime Minister, and his ship was sunken by the fleet commander. This angered the captains of the Sovremenny class destroyers Gumrak, Chuda and Dub and they quickly headed out to aid the Kestrel Fleet.
Anderson, recognizing that these three Yuke ships were defecting, ordered the Kestrel Fleet to engage the Nationalist Yuke Fleet and defend the friendly Yuke ships. The Kestrel launched its only four pilots, the Ghosts of Razgriz, to assist in the fight. The Yuktobanian aircraft carrier Admiral Tsanev launched aircraft of its own.
About halfway through the battle, a fleet of nationalist Osean ships stumbled upon the fray. After listening in for a moment, the Osean commander decided that the Kestrel Fleet had betrayed Osea and sided with the Yukes. He then ordered his fleet to engage, therefore making the battle three-way.
After a hard-fought battle, the Nationalist Yuktobanian and Osean Fleets were completely wiped out, with all ships sunk. The Kestrel Fleet, with its new Yuke allies, was now completely separate from the OMDF.
This turned out to be the last battle of the aircraft carrier Kestrel. The next day, an unidentified Yuktobanian submarine launched two anti-ship missiles at the Kestrel, which both scored direct hits. Though the Razgriz pilots were able to get off the carrier safely, the ship was sunk. From one of the lifeboats, Anderson stated that he had lost time and time again, but as long as the Razgriz were still flying, he had won.