- Previous: Third Battle of Earth
- Concurrent: Battle of Sinope
- Next: Battle of Ceres
- War: Neosapien War
- Year: 2120
- Location: Io
- Pirate Clans
- Neosapien Commonwealth
- Commanding officer
After the near destruction of Exofleet, Winfield sent J.T. Marsh and Alec DeLeon to negotiate an alliance with the Pirate Clans. Although he realized it was a desperation tactic, it was his only chance to gain time and reinforcements. Winfield remained on Io for a conference of the leaders of the Earth Resistance and the Venus Resistance.
The Earth Fleet, under the command of Typhonus, had been sent to destroy the Exofleet base in the Outer Planets. After the resistance leaders had been picked up by the Arnhem, Phaeton ordered Typhonus to follow the Arnhem to the Exofleet base.
Typhonus followed the Arnhem to Io and proceeded to attack the Arnhem. Winfield ordered a counterattack using everything available, including the GRAF Shield. The Neosapiens retreated after the shield destroyed a fighter, but the premature activation overloaded the shield. Typhonus wanted to overwhelm the Io GRAF Shield with sheer numbers, but Phaeton ordered him to lay siege. Exofleet would be forced to escape or starve without their supply lines. Typhonus was sent to Tethys to prevent the pirates from allying with Exofleet.
Although Winfield was able to bluff the Neosapiens into believing the shield was operational, he knew time was running out for Exofleet. On Tethys, Marsh failed to convince Simbacca to ally with Exofleet, even though he won a duel against Jubail. On Io Winfield was having similar trouble with the resistance leaders. The situation initially became worse when Typhonus arrived at Tethys, but that turned into an advantage when Typhonus kidnapped Simbacca to demoralize the clans.
Marsh and DeLeon used Hallas as a decoy to board the Neosapien flagship. Simbacca was shocked that the rescue mission had been orchestrated by Marsh. Jubail ordered an attack on the Neosapiens after Simbacca shamed them with the fact that Exofleet was fighting the Neosapiens more effectively than the pirates. The pirate attack broke the Neosapien infantry perimeter inside the flagship, allowing them to escape.
The pirate attack on the outside damaged the reactor’s containment and Typhonus ordered the flagship abandoned. Returning to Tethys, Simbacca announced that the clans would ally with Exofleet and ordered the pirate fleet to Io. Typhonus ordered a return to Io while Phaeton lectured him on his incompetence. He then revealed the existence of the Fusion Pulse Cannon, used during the Battle of Sinope.
The debris from the Battle of Sinope damaged the Earth Fleet and forced Typhonus to withdraw from attacking the pirate fleet. Soon after the pirates arrived at Io, Typhonus contacted Barca and ordered him to disable the GRAF Shield. During the negotiations Simbacca agreed to surrender the pirate bases on the Outer Planets in exchange for Mars. He also revealed the existence of Chaos.
Typhonus was informed by Barca that the shield was inoperative and sent in his fleet for a decisive attack. Winfield ordered an immediate evacuation of the base and sent the E-frames to delay the Neosapiens. Both sides lost ships, but Io was evacuated. Winfield ordered the fleet to scatter, but Simbacca told him that he already had a course prepared. As the Earth Fleet gained on them, Winfield prepared to transfer the E-frames while Exofleet would fight a defensive battle so the pirates could escape.
However, Simbacca had repeated his tactics used during the Pirate Clans War and ambushed the Neosapiens. After losing several ships, Typhonus ordered a withdrawal. On Mars Typhonus was executed and replaced with a clone. Exofleet and the Clans arrived at Chaos.