Eventually, he and Heero made it back to Earth, where they met with Lucrezia Noin, an ex-OZ pilot instructor who now worked with the ruler of the pacifist Kingdom of Sanc, Relena Peacecraft. With tensions growing between Sanc and the Romefeller Foundation (a group of aristocrats and royalties from across the world which had been secretly manipulating world affairs for centuries), Quatre left for the Middle East once more, in search of the newly rebuilt Sandrock. He returned to the kingdom with the Maganacs and provided defense from the invading Romefeller Foundation. Not wanting to see her people suffer any longer, however, Relena surrendered the kingdom and gave herself up to the Foundation. With no other options, Quatre returned to space.

He took temporary refuge on his home colony, within the Winner Corporation, and searched for the other pilots. Not much later, Duo sought him out and informed him that Trowa was alive and gave him his location. Quatre soon found him at the circus, which the other pilot had previously been using as his cover, only to realize that Trowa had amnesia. Quatre tried to get through to him, but Trowa's "adopted" sister, Catherine Bloom, made it clear that Quatre's presence wasn't welcome, as Trowa was much happier away from the war. Quatre explained that Trowa's current state was all his fault, and although his apology wouldn't be enough, it was the only thing he could do at the moment.

As he prepared to leave the colony, a battle between OZ and a rebel colony group called White Fang spread into the area. He returned to the circus to warn Catherine and Trowa and then set out to fight in order to protect the colony. Something must have gotten through to Trowa, though, because he felt that Quatre was calling him (which is perhaps another function of the "space heart") and soon joined him and Noin in battle. The three were later saved by Duo when they were mistaken for White Fang members, and their group was recovered by Duo's fellow sweeper, Howard, who was commanding the battleship Peacemillion. While on board, Quatre's Gundam was upgraded for space battle.

Later, when White Fang engaged OZ in battle outside of the space fortress Barge, Quatre, Trowa, and Duo intervened, taking neither side, and watched as White Fang leader Milliardo Peacecraft single-handedly took out the entire fortress by causing a chain reaction of explosions. With the balance of power in space now in White Fang's favor, OZ took the residents of the colony Trowa's circus troupe was on hostage, demanding that Libra (an OZ battleship that White Fang had seized) be returned. Milliardo made the decision to blast the colony with Libra's cannon instead, or at least made everyone believe that was what he'd been planning. In reality, the cannon was aimed for Earth, and it caused a massive amount of destruction when it was fired.

Determined to stop Milliardo, the pilots battled with White Fang's mobile dolls (mobile suits that were made to be controlled remotely, thus not risking the pilots' lives) before returning to Peacemillion, exhausted and with damaged suits. At Heero's request, the engineers installed the ZERO System into Quatre's Gundam so he would be able to lead the other pilots. Although Quatre protested vehemently, afraid that he would lose himself to the system again, Heero had faith that he could master it and insisted that he try.

When the pilots went up against the mobile dolls again, they noticed that the dolls' strategy was far too calculated to be mere programming. It became clear that someone else was controlling them, so Quatre was forced to use ZERO to bring the pilots together and strategize. It turned out that the mobile dolls were being controlled by Dorothy Catalonia, Milliardo's right hand, using a modified ZERO System. Fortunately, Quatre was able to best Dorothy in a battle of tactics, and the Gundam pilots defeated the dolls. After returning to Peacemillion again, Quatre removed ZERO, deciding that he no longer needed it; he had confidence in his own tactical abilities.