The Orb Union space colony, Heliopolis, is attacked by ZAFT, despite its neutrality since the beginning of the Bloody Valentine War. Kira Yamato accidentally sees the Earth Alliance's new prototype mobile suits, which have been secretly constructed at the Heliopolis Morgenroete factory. He encounters his childhood friend, Athrun Zala, now a ZAFT soldier as one of the attackers.

ZAFT is able to steal four of the five G Project prototype mobile suits, leaving only the GAT-X105 Strike. With Murrue Ramius unable to pilot it effectively, Kira pilots the Strike and defends Heliopolis against the invading ZAFT forces to protect his friends. Ensign Natarle Badgiruel takes command of the new mobile assault ship Archangel with the surviving crew members.

Lt. Murrue Ramius takes over as captain of the Archangel and Kira and his friends are detained for seeing top secret military weapons. Rau Le Creuset is determined to capture the Strike after seeing how well it moved and sends out mobile suits to retrieve it. Disobeying orders, Athrun also dispatches so he could confirm if Kira is the one piloting the Strike, but when he finds his answer, Heliopolis crumbles as it sustains too much damage.

Kira discovers a malfunctioning lifeboat and brings it aboard the Archangel. Everyone is surprised to find Flay Allster as one of the rescued civilians. The Archangel decides to head for the Eurasian Federation military satellite Artemis to seek help. Rau Le Creuset follows and plans an attack on the Archangel. Kira decides to continue piloting the Strike and his friends volunteer to become members of the Archangel crew as his support.

Mu La Flaga and Kira launch a counteroffensive against the ZAFT ship Vesalius. The Strike's Phase Shift Armor runs out of power in the middle of the battle and Athrun uses this moment to grab the Strike so he can take Kira with him, but Kira frees himself with Mu's help.

The Archangel and its crew are held captive by the Artemis forces. Nicol Amalfi in his GAT-X207 Blitz attacks Artemis, using its Mirage Colloid armor to remain effectively invisible and destroys the Umbrella of Artemis, which protects the asteroid fortress. During the attack, the Archangel is able to escape.

The Archangel forages for water in the Debris Belt. They are shocked to find themselves in the ruins of Junius Seven, so the crew decides to hold a memorial. As they are excavating ice found around the ruin, a ZAFT mobile suit attacks, but Kira dispatches him. Kira finds a floating lifepod and takes it aboard.

Lacus Clyne, the daughter of PLANT Supreme Council Chairman Siegel Clyne, is found within the lifepod. Her presence causes tension within the crew, but when the crew receives a message from the 8th Fleet that they are being searched and rescued, they are overjoyed.

The Archangel is to meet with the 8th fleet but is attacked by the Le Creuset Team. Flay witnesses the death of her father when Kira fails to protect the escort ships. In desperation, the Archangel reveals Lacus is on board the ship, causing the attackers to withdraw.

With everything that has happened, Kira becomes depressed. He is comforted by Lacus, who is strolling around the ship without permission. Kira returns Lacus to Athrun against orders, but refuses Athrun's invitation to change sides.

Le Creuset launches an attack on the Archangel. Kira's desire to protect his friends awakens an unknown almost berserker ability. He single handily defeats the attacking Blitz, GAT-X103 Buster, and GAT-X102 Duel.

Kira and his friends are given permission to leave the Archangel, but after overcoming the initial shock of her father's death, Flay decides to enlist in the Earth Alliance Forces, prompting Sai Argyle, Kuzzey Buskirk, Miriallia Haw, and Tolle Koenig to do the same. Kira stays on board the as well to continue protecting his friends. Duel Gundam is upgraded with an Assault Shroud.

Rau Le Creuset reflects on the events that took place in episodes one to thirteen and the Coordinator's history starting from the birth of the first Coordinator, George Glenn.

The Archangel saves Kira as they enter the Earth's atmosphere. As a result, they land in ZAFT-controlled territory in the Sahara in northern Africa, far from their intended target, Alaska. Flay begins to take care of Kira and comforts him when he is tormented by the memories of the spacecraft that was destroyed in the previous battle.

The Archangel is attacked by multiple TMF/A-802 BuCUE units. Kira hastily takes off and fights the ZAFT forces, but he is unfamiliar with the desert environment. His ability to adapt amazes ZAFT's commander Andrew Waltfeld. When the Strike is about to run out of power, a resistance group comes to his aid and lures the remaining BuCUE units into an explosive trap.

Murrue Ramius thanks the resistance group for their help and agrees to be allies. The resistance group introduces themselves as the Desert Dawn who are fighting Andrew and the Lesseps. Kira once again meets with Cagalli Yula Athha, the mysterious young woman he first encountered at Heliopolis' Morgenroete factory, who is now part of Desert Dawn. Meanwhile, Andrew attacks the Desert Dawn's hometown, but evacuates the town first.

Though the Desert Tiger has spared the lives of civilians, Desert Dawn members brashly challenge the ZAFT forces, because of the devastation they caused. The attack ends in failure, but most are saved by Kira in the Strike.

Kira and Cagalli are sent into a nearby ZAFT controlled city to gather supplies with Natarle and the Desert Dawn. The two teenagers get caught in an attack by the Blue Cosmos, and when Kira saves a man who happens to be Andrew Waltfeld, they are invited to the ZAFT base. There, Andrew reveals that he knows Kira is the pilot of the Strike and a Coordinator, but lets them leave safely.

Athrun and Nicol are given the day off; Athrun spends the day with Lacus and they talk about Kira. The PLANT Supreme Council debates on whether the attack codenamed "Operation Spitbreak" should be executed

A battle between the Lesseps and the Desert Dawn commences. Kira and the Desert Tiger fight a battle where they realize the pain of having an enemy who is not an abstraction. With the Strike's power almost depleted, Kira has no choice but to destroy Andrew's TMF/A-803 LaGOWE or die himself.

The Archangel crew crosses the Red Sea to head towards the neutral Orb Union with Cagalli and Ledonir Kisaka on board. With the previous battle weighing heavily on him, Kira talks to Cagalli about his reasons for fighting, making Flay jealous. They are attacked by ZAFT air and underwater type mobile suits, but Kira and Mu manage to take them out.

A battle with ZAFT submarine forces led by Commander Marco Morassim prevents Kira from fighting alongside Mu and Cagalli in their FX-550 Skygraspers. Cagalli's Skygrasper sustains damage and is forced to turn back, but she encounters Athrun's transport plane; her Skygrasper is shot down, but not before shooting down his transport plane, forcing Athrun in his Aegis to eject from the transport plane. By chance, they are both stranded on the same deserted island.

Cagalli is surprised to find Athrun on the same deserted island. She attacks him, but she is overpowered and captured. When everything settles down, the two discuss the war and the reason why they are fighting. At sunrise, they are rescued by their respective comrades.

The Archangel is attacked by the Zala Team which consists of the Le Creuset Team members. They take heavy damage, but when they enter the waters of the neutral nation of Orb, ZAFT is chased away and is told that the Archangel has been chased away. The Zala Team sneaks into Orb with the belief that Orb's official statement is false.

A recap of the first 25 episodes narrated by Miguel Aiman.

Senior Engineer Erica Simmons of Morgenroete reviews the Strike's combat logs and theorizes that Kira might be superior than any other Coordinator and speculates on the "SEED factor" theory. She shows Kira the mobile suits that Orb is developing and asks him to develop a mobile suit operating system that can be used by Naturals.

Kira and his friends are given the chance to meet with their parents who have taken refuge in Orb. Kira refuses to go, but his parents meet with Uzumi Nara Athha who hints there is a deeper connection between Kira and Cagalli. Kira instead completes the operating system for the Orb Union's MBF-M1 Astrays. When Kira's mechanical bird flies off, Kira finds himself standing face to face with Athrun. They part ways pretending not to know each other, but not without saying kind words about each other.

The Archangel, without Cagalli and Ledonir on board, leaves Orb territory for Alaska. The Zala Team, who is patiently waiting, engages them in a battle. Kira grounds the Duel, Buster, and Blitz with the help of Mu and Tolle, who is now the second Skygrasper pilot. As Kira and Athrun fight, Nicol intervenes, but he steps into Kira's fatal attack.

The Zala Team make another effort to destroy the Archangel and the Strike. Dearka in the Buster is shot down by Mu and surrenders. Tolle attempts to aid Kira, but he is killed by Athrun. The grief Kira and Athrun suffer over their friends' death is enough for them to try to kill each other.

The crew of the Archangel grieve for the apparent deaths of Kira and Tolle. Cagalli searches the wreckage for Kira but instead finds Athrun and confronts him for killing Kira.

The Archangel finally arrives in Alaska. A grief-stricken Miriallia attacks Dearka, now a prisoner on board the Archangel, but ends up saving his life when Flay tries to shoot him. Kira awakes and finds himself in the care of Lacus.

The crew of the Archangel find themselves questioned for their actions regarding their escape from Heliopolis, the fall of the 8th Fleet, and entrusting the Strike to Kira Yamato. Meanwhile, Lacus comforts Kira, who questions his right to live, especially after trying to kill Athrun.

Flay, Mu, and Natarle are to be transferred off the Archangel. Mu suspects that something is not quite right as the Alaskan JOSH-A base is evacuated. Flay is captured by Rau Le Creuset. Lacus and her father entrust Kira with the ZGMF-X10A Freedom, equipped with Neutron Jammer Canceller technology.

Operation Spitbreak is initiated, with both ZAFT and the Earth Alliance believing they have outsmarted the other. The Archangel is left behind to be destroyed in a calculated plan that would decimate everyone on the battlefield, until Kira arrives to save them.

Lacus, now denounced a traitor to the PLANTs for handing the Freedom over to an unknown pilot, confronts Athrun and challenges him to decide what he truly is fighting for. Athrun is ordered to pilot the ZGMF-X09A Justice to seek and destroy the Freedom.

Kira and the Archangel make their way to Orb, where Lord Uzumi welcomes them and asks that they decide for themselves why they are fighting. The Panama mass driver is destroyed by ZAFT in retaliation for the blow they took at Alaska. Meanwhile, Erica Simmons presents a reconstructed Strike for the Archangel crew's use.

To get a hold of Orb's mass driver, the Earth Alliance demands Orb to concede with them or be attacked for siding with ZAFT. Murrue decides the Archangel will support Orb and its crew members are discharged if they no longer wish to fight. Muruta Azrael, leader of Blue Cosmos, attacks Orb with three new mobile suits, the Forbidden, Raider, and Calamity. When Kira starts to have trouble with them, Athrun in the Justice arrives to help.

Athrun in the Justice assists Kira fight against the Forbidden, Raider, and Calamity. As the fight continues, the three Earth Alliance pilots argue with one another, but they are interrupted when they are struck by intense pain. The Earth Alliance are forced to retreat and regroup. The two friends reunite and Athrun must make a decision regarding whether he should continue obeying his father's orders or fight for what he believes in.

The Earth Alliance attacks again, but the results are the same as the previous battle. The Archangel and the Orb ship Kusanagi launch into space, while the leaders of Orb stay behind. They explode Orb's mass driver and armaments factories, sacrificing their own lives in the process.

Cagalli, though grief striken with her father's death, confronts Kira with a mysterious photograph given to her by Lord Uzumi, of a woman with two infants and Kira and Cagalli's names written on the back. On a PLANT, Lacus is still on the run for treason, but broadcasts messages to counter PLANT Supreme Council Chairman Patrick Zala's propaganda. She soon discovers that her father has been assassinated by Patrick Zala.

Athrun returns to the PLANTs on a shuttle to speak to his father, but he is arrested. Lacus and (the presumed killed in action) Andrew Waltfeld join forces, stealing the ZAFT support ship Eternal and rescuing Athrun. They join forces with the Archangel and the Kusanagi thus forming the Three Ships Alliance.

The newly-formed Three Ships Alliance take shelter at the abandoned Mendel colony. Unfortunately, they are tracked down by both ZAFT and Earth Alliance forces. Rau Le Creuset commands the ZAFT fleet and Captain Natarle Badgiruel, commands the Earth Alliance assault ship Dominion. Dominion takes the initiative and attacks with the mission of capturing either the Freedom or Justice.

The Dominion retreats so their pilots can get their medicine. Mu and Dearka enter the Mendel colony to confront Rau and Yzak. Kira comes to their aid and he and Mu are shocked to discover Rau has a few secrets to reveal.

Kira and Mu face terrifying revelations in an encounter with Rau. Dearka and Yzak have their own meeting where they question what they are truly fighting against. Meanwhile, the Dominion and the Earth Alliance once again attacks. Rau returns to his ship and sends Flay back to the Earth Forces.

Flay, who was held captive by Rau, is rescued by the Dominion despite Kira's desperate attempts to steal her lifepod. She gives Muruta Azrael the disk she was given by Rau which contains the specs on the Freedom and Justice and the Neutron Jammer Canceller technology.

Equipped with Neutron Jammer Cancellers, the Earth Alliance forces launch an all-out attack on the PLANTs. The Boaz military asteroid is destroyed by nuclear weapons with Earth Alliance's next target being the PLANTs. The Freedom and Justice arrive at the battlefield in time to destroy all the nuclear warheads. In retaliation, Patrick Zala orders to fire the GENESIS.

The GENESIS, a huge gamma-ray laser wipes out a large portion of Earth Alliance's forces. The Earth Alliance forces are forced to withdraw temporarily to regroup. During the intermission, each of the couples on board the Archangel, Kusanagi, and Eternal prays of each others safety in the upcoming battle.

GENESIS' second attack cripples the Earth Alliance's reinforcements and destroys their Ptolemaeus lunar base. The Three Ships Alliance save the PLANTs from the second wave of nukes. Mu fights Rau in the ZGMF-X13A Providence while Kira and Athrun fight the Forbidden, Raider, and Calamity. On the Dominion, Natarle becomes fed up with Muruta and orders the crew to escape. Muruta fires at the Archangel , but Mu sacrifices himself to protect them. In revenge, the Archangel fires and destroys the Dominion.

The Archangel, Eternal, and Kusanagi plunge into the battle, trying to keep both sides from using their weapons of mass destruction. Rau destroys Flay's escape shuttle, killing everyone on board. Flay's spirit visits the grief striken Kira to apoligizes and thanks him. Kira destroys the Providence with the Freedom, while Athrun remote-destructs the Justice to destroys GENESIS. With both the PLANTs and the Earth Alliance forces in disarray, the renegade moderate faction of the PLANTs seize the opportunity to call for a cease-fire, effectively ending the war.