- Previous: Second Battle of Venus
- War: Neosapien War
- Location: Earth
- Tactical victory: Neosapien Commonwealth
- Strategic victory: Neosapien Commonwealth
- Neosapien Commonwealth
Three months after the Second Battle of Venus, Furlong and Matthew Marcus were were demanding action, having become dismayed at Winfield's construction and repair program. Winfield rejected an immediate attack since Exofleet lacked the firepower to win, although he knew that the Neosapiens had access to more drydocks and were looking for Algernon's sabotage to the GRAF Shield.
Marcus and Furlong then decided to commit mutiny, but Marcus took precautions to remove Winfield's support among the officers. He ordered Able Squad to Mars to destroy a weapons complex near Olympus Mons. The E-Frame Dropship was detected in orbit, forcing Able Squad fight their way down to the surface. Marcus then ordered the dropship to return to Io.
After destroying the cloning complex, Able Squad contacted the Resolute for an extraction ship. Winfield was baffled about the situtation until Marcus and Furlong appeared and seized control of the bridge. Marcus then took control of the entire fleet and Io base. Taken by surprise, Winfield's supporters were easily captured. Many in Exofleet showed enthusism about the upcoming battle, which they believed would be the decisive clash.
When informed of Exofleet's intentions, Phaeton realized that the Neosapien's superior numbers would allow them to destroy Exofleet. As the fleets came into visual range, Marcus was stunned that the Mars Fleet, on the right flank; was as large as the Earth Fleet, on the left flank. Marcus decided to continue with the attack despite being surrounded.
The battle immediately tilted in favor of the Neosapiens as Exofleet lost several support ships. The Resolute was subjected to heavy bombardment and suffered severe damage. Marcus finally realized the battle was lost and ordered the crew to abandon ship. Numerous other Exofleet ships were destroyed as well. Marcus remained on board the Resolute and armed all of the warheads for a kamikaze run against the Neosapien fleet. The resulting explosion destroyed numerous Neosapien ships.
Winfield, who had retaken command of the fleet, ordered all ships to escape. Boarding the Dominion, he relieved Furlong of command and repeated the withdrawal order. After returning to Io, Winfield told Marsh that Exofleet had lost too many ships to challenge the Neosapien fleet. He ordered Marsh to contact the Pirate Clans for an alliance.