Mobile Suit Gundam SEED, MBS/TBS
ANN; GundamOfficial (archived); Gundam Wiki; IMDb; Madman; Toonami Wiki; TV.com; TV Tropes; Wikipedia
50 episode series made in 2002-2003, and set in the year Cosmic Era 71. I want to warn you again that there may be a lot of spoilers in this entry, though the first three paragraphs after this one will be pretty safe. Anyway, most of this is just stuff I've learned through online resources, so rather than giving things away, it should mostly just help you keep track of what's going on when you watch the show. I know I had a hard enough time following everything, especially in battles when there were too many Gundams for me to keep track of. Not to mention all the subtle plot points and backstory... Still, as complicated as it all was, I thought it was a pretty damn good story.
Well... I think this series was kind of a remake of the original series, but with different characters and situations, but it's basically pretty similar, if more modern, complex, better written, with more interesting characters, and way better drawn. The Earth Alliance is at war with ZAFT, which is the military forces of some space colonies called PLANTs (Productive Location Ally on Nexus Technology). I guess "PLANT" now refers to the group of colonies, controlled by Coordinators, as an independent nation; and to civilians of that nation. The war mainly seems to be about Coordinators against Naturals. (Coordinators are basically like the original series' Newtypes, except that their enhanced abilities have been genetically engineered into them, rather than occurring naturally.) There is a theoretical factor called SEED (Superior Evolutionary Element Destined-factor), an ability which may be possessed by Naturals or Coordinators, which is practically essential to pilot Gundams effectively. Anyway, the war began in CE 70, when Earth forces used nuclear weapons against the PLANTs on the agricultural colony Junius Seven, in what will be known as the Bloody Valentine tragedy. Not long after this, the PLANTs begin using N-Jammers, which make it impossible to use either nuclear weapons or nuclear power.
The series begins 11 months later. The main character is Kira Yamato, a teenaged Coordinator whose parents are Naturals. He's a lot like Amuro from the first series. He was a student on the neutral colony of Heliopolis, until it was attacked by ZAFT. A munitions corporation called Morgenroete, based in the neutral Earth-based nation of Orb as well as Heliopolis, had secretly been working with the Earth Alliance to develop new mobile suits called Gundams, as well as the warship Archangel, at Heliopolis. Actually, unlike other Gundam series, the mobile suits aren't really called Gundams in this one; it's a name Kira made up when reading "General Unilateral Neuro-link Dispersive Autonomic Maneuver system," but they're actually called GAT-X (Gressorial Armament Tactical-eXperimental) series mobile suits. ZAFT forces managed to steal four prototype Gundams: the Aegis, Duel, Buster, and Blitz. Earth forces retain one Gundam, however, the Strike, which Kira ends up piloting for them. He and some other civilian kids, friends of his- Flay Allster, Sai Argyle, Miriallia (Mir) Haw, Tolle Koenig (Mir's boyfriend), and Kuzzey Buskirk- are evacuated from Heliopolis (along with other civilians), on the Archangel (which is pretty similar to the original series' Whitebase).
Its acting captain is Murrue Ramius, a lieutenant who was the senior surviving officer after ZAFT's attack. She often clashes with the ship's more aggressive combat commander, Natarle Badgiruel. The crew also includes a mobile armor (more like a plane than a suit) pilot named Mu La Flaga, a well-respected war hero, who becomes interested in Captain Ramius. Anyway, the Archangel is undermanned, so Kira's friends help out with some duties. The Archangel is being pursued by a ZAFT ship called the Vesalius, and its escort, the Gamow. The team is under the command of Rau Le Creuset (who considers Mu his archenemy), who wears a mask like Char did in the original series. The stolen Gundams stay with the task force led by Le Creuset, piloted by four young Coordinators. One of them is Athrun Zala, an old friend of Kira's, who doesn't understand why Kira is fighting on the side of the Naturals; he pilots the Aegis. The others are Yzak Joule, who pilots the Duel; Dearka Elsman, who pilots the Buster; and Nicol Amalfi, who pilots the Blitz. Kira, for his part, doesn't want to be involved in the war at all, but he feels the need to protect his friends.
After one battle, Archangel rescued a lifepod containing Lacus Clyne, who is engaged to Athrun. She's the daughter of Siegel Clyne, chairman of the PLANT Supreme Council. She befriended Kira, who later returned her to Athrun. She really wishes Athrun and Kira could go back to being friends, instead of being forced to fight each other in the war. Anyway... at one point, Flay's father is killed in a battle. He was an important diplomat (but then, it seems like so many of these characters are related to important military or political leaders, on both sides). Flay hates Coordinators, wants them all to die. For a time this seemed to include Kira, but then she started dating him (much to the chagrin of her former fiancee, Sai). It's apparent she's just using Kira, wants him to kill his fellow Coordinators in battle, but he doesn't see this, because he's always had a crush on her. (This relationship won't last, but it will have lasting emotional effects on various characters.)
Eventually the Archangel gets to Earth, and spends some time in the desert battling a ZAFT group led by Andrew Waltfeld, aka the Desert Tiger. The Earth forces team up with guerillas known as Desert Dawn, who are fighting ZAFT for control of their city. Among them is a girl named Cagalli Yula Athha, whom Kira first met when Heliopolis was under attack. Flay will of course become jealous of her, even though Kira and Cagalli usually don't seem to get along that well. Anyway, the Archangel eventually winds up in Orb. This is Cagalli's homeland, and she remains behind when the ship departs.
Then Kira kills Nicol in battle, and Athrun kills Tolle. Then Kira and Athrun battle, and it seems they kill each other. Both their Gundams are destroyed. Dearka gets captured by the Archangel, and while imprisoned on board, he gets to know Mir, who at first hates him, but later... not so much. The Archangel continues on to Earth's JOSH-A (Joint Supreme Headquarters Alaska, pronounced "Joshua") base, where La Flaga, Badgiruel, and Flay receive reassignments.
Anyway, it turns out Kira is alive, and cared for by Lacus, who gives him ZAFT's new Gundam, the Freedom. She'll get in trouble for this, of course. Kira doesn't want to fight for Earth anymore, he just wants to fight for peace. Meanwhile, Athrun was being cared for in Orb, by Cagalli. When he returns home, he's given ZAFT's other new Gundam, the Justice, in order to pursue Kira. (Both new Gundams have N-Jammer Cancelers, which could prove disastrous to the PLANTs if they ended up in Earth hands.)
The Earth forces mass most of their forces at Panama, which ZAFT is supposedly going to strike, but instead they strike JOSH-A. However, Earth had their own plan- they blew up their own base, taking out a huge chunk of ZAFT's forces, as well as their own. Flay is captured by Le Creuset. La Flaga ends up back on the Archangel. The Archangel barely escapes when La Flaga warns them of the Earth Alliance's plan, and the Alliance now considers them renegades, for failing to remain in the battle.
Athrun's father, Patrick Zala, becomes chairman of the PLANT Supreme Council, and wants to destroy all Naturals. He orders Siegel and Lacus Clyne to be arrested as traitors. Siegel starts the Clyne Faction to oppose Zala's radical leadership, but he's eventually killed, and Lacus carries on his campaign, from the underground. The Archangel returns to Orb. Kira rejoins them, in the Freedom. Meanwhile, ZAFT attacks Panama, destroying the Alliance's last mass driver, so they can't get into space. Muruta Azrael, the leader of Blue Cosmos, an anti-Coordinator group, now seems to be in control of the Earth Alliance forces. He wants to destroy all Coordinators, and also gets the Alliance (particularly the Atlantic Federation) to try to force Orb (along with its mass driver) and the few other remaining neutral nations to join the Alliance, but Orb refuses.
Earth has some new Gundams that can be operated by artificially enhanced Naturals (called biological CPUs, who are classified as equipment rather than pilots). These include the Calamity, piloted by Orga Sabnak; the Forbidden, piloted by Shani Andras; and the Raider, piloted by Clotho Buer. Azrael pits these Gundams against Orb; the Archangel will fight alongside Orb, against the Earth forces. Kuzzey and some other crewmembers depart the Archangel to evacuate along with Orb's civilians, before the battle. La Flaga now pilots the rebuilt Strike. Also, Dearka was released, and then he reclaimed his Buster Gundam, and decided to fight on Orb's side. Athrun also joined Orb's side, with the Justice. Cagalli pilots a new mobile suit, the Strike Rouge. Orb also has a few Astray Gundams, piloted by Asagi Caldwell, Juri Wu Nien, and Mayura Labatt. To ensure the mass driver doesn't fall into Earth's hands, Lord Uzumi Nara Athha, head of Orb's government, destroys the mass driver and Morgenroete's factories, but not before sending Cagalli into space aboard the warship Kusanagi, alongside the Archangel, as well as revealing a secret about Kira and Cagalli (though I had guessed it quite awhile ago), which I won't spoil for you.
Meanwhile, Earth captures the Victoria spaceport, and Badgiruel is given command of a new ship called the Dominion- though she is forced to constantly follow the orders of Azrael, who goes along on the ship, along with his new Gundams and biological CPUs. Athrun returns to ZAFT to confront his father, and is arrested. The Clyne Faction, including Andrew Waltfeld, rescue Athrun. The two of them, along with Lacus and her followers, escape into space on the warship Eternal, and join the Archangel and Kusanagi. The Three Ships Alliance will have to fight both ZAFT and the Earth Alliance- including the Dominion. Le Creuset's ships are sent after the Eternal, and he ends up fighting Mu and Kira on an abandoned colony, as well as telling them some shocking things Mu doesn't want to believe.
Later, back in space, Le Creuset sets Flay adrift in a lifepod, and she is rescued by the Dominion. He sent with her a "key to end the war," which she handed over to Azrael. It turns out to be specs for N-Jammer Cancelers, so Earth can now use nuclear weapons against the PLANTs. This forces ZAFT to unveil its own superweapon, GENESIS (Gamma Emission by Nuclear Explosion Stimulate Inducing System). The Three Ships Alliance is caught in the middle, trying to prevent both sides from using their nuclear weapons. Le Creuset pilots ZAFT's new Providence Gundam in the final battle. All of humanity, Naturals and Coordinators alike, stands on the brink of destruction, which seems to be Le Creuset's wish. And that is all I want to say about the series. The end comes pretty soon after we get to this point, and I don't want to spoil it for you, even if it's not exactly unpredictable....
There are also some side stories (mostly manga) which I don't really know anything about, called "Gundam Astray," and a sequel series called "Gundam SEED Destiny," which I haven't seen, but would really like to eventually. There might be even more stuff, like a movie or OVAs or whatever, I'm not really sure....