The story centers around the Green Lanterns of Earth—Hal Jordan, Kyle Rayner, John Stewart and Guy Gardner—and the rest of the Green Lantern Corps as they fight an interstellar war against the Sinestro Corps, an army led by the former Green Lantern Sinestro who are armed with yellow power rings and seek a universe ruled through fear. A 1986 Alan Moore "Tales of the Green Lantern Corps" story was the thematic basis of the storyline. Many characters were changed, killed off or re-introduced as a result of the event.
Critical and fan reception to "Sinestro Corps War" was highly positive. Many reviewers ranked it among the top comic books of the year and the storyline's first issue garnered a 2008 Eisner Award nomination for Best Penciller/Inker or Penciller/Inker Team. The storyline was also a financial success, and several issues underwent multiple printings. "Sinestro Corps War" is the second part of a trilogy in the Green Lantern storyline, preceded by the 2005 miniseries Green Lantern: Rebirth. The conclusion of "Sinestro Corps War" sets up the third and final part of the trilogy, Green Lantern: The Blackest Night, which is scheduled for publication in 2009.
Following his defeat in Green Lantern: Rebirth, the events of Green Lantern: Sinestro Corps Special #1 see the supervillain Sinestro retreat to the planet Qward in the Antimatter Universe. There he amasses an army, the Sinestro Corps, that he selects based upon their ability to "inspire great fear". Each member is armed with a yellow power ring, mirroring the green ones of the Green Lantern Corps. Amongst Sinestro's allies are Parallax and the resurrected Anti-Monitor. The Sinestro Corps then launch an all-out assault against the Green Lantern Corps and the universe itself.
During the assault on Oa, the Sinestro Corps manages to inflict heavy casualties and free Superman-Prime and the Cyborg Superman from their imprisonment. Kyle Rayner is captured and transported to Qward, where Sinestro manages to separate Rayner from the symbiote Ion allowing Parallax to possess him. In Green Lantern (vol. 4) #21 the heroes Hal Jordan, John Stewart and Guy Gardner attempt to rescue fallen comrade Kyle Rayner, but are themselves entrapped, with Jordan transported to face Sinestro and his allies. A failed bid to rescue Jordan depicted in Green Lantern (vol. 4) #22 sees surviving members of the Green Lantern Corps forced underground and split into two groups. While one group attempts to free Jordan only to find themselves ambushed, the other successfully rescues Ion. They then re-unite with their ambushed comrades and together they escape from Qward back to the positive matter universe. Hal, John and Guy return to Earth to warn the Justice League of the Anti-Monitor’s return.
As the Sinestro Corps spreads out to ambush Green Lanterns across the universe, Green Lantern (vol. 4) #23 sees the Guardians decide to rewrite their sacred text, the Book of Oa. They remove a section devoted to a prophecy concerning the “Blackest Night”, against the objections of two of their number, Ganthet and Sayd. They then add 10 new laws, the first of which authorizes the use of lethal force against the Sinestro Corps, while Ganthet and Sayd are expelled from Oa. As the Green Lanterns gather on Oa in preparation for a Sinestro Corps assault, the Sinestro Corps teleport themselves and their Central Power Battery instead to a new Warworld, their objective revealed to be Earth. Events in Green Lantern Corps (vol. 2) #16 show Hal informing the Green Lantern Corps of Sinestro's plans.
Green Lantern (vol. 4) #24 continues the story, with Green Lanterns and Sinestro Corps members battling across Earth. Hal manages to free Kyle from Parallax before the entity is imprisoned in their power batteries by Ganthet and Sayd. After John and Guy arrive, the former Guardians reveal to them the prophecy of the “Blackest Night”, seen in Green Lantern (vol. 4) #25. It foretells of five more Corps arising, each based on a different color and emotion. After the five corps are established, a "War of Light" will ensue, in which all the corps are destroyed, leading to the “Blackest Night”.
The Guardians arrive on Earth and appoint Sodam Yat to be the new Ion. After a lengthy struggle in New York, the Sinestro Corps are defeated by the overwhelming numbers against them. One of the Guardians sacrifices himself to send Superman-Prime to an alternate universe, while Hal and Kyle subdue and arrest Sinestro in Coast City. In the aftermath of the battle, seen in Green Lantern (vol. 4) #25, the Guardians decide to bring the second of the new laws into effect. After realizing that the "Blackest Night" prophecy will come to pass, Ganthet and Sayd depart after creating a blue power ring with the intention of creating their own Corps, based on the spreading of Hope to the rest of the universe. The Anti-Monitor, having been blown across the vacuum of space at the battle's climax, finds itself on a dark planet. Here it is transformed by an unknown force into a Black Power Battery.
"Sinestro Corps War" was based on concepts introduced by Alan Moore and Kevin O'Neill in the short story Tygers, published in Tales of the Green Lantern Corps Annual #2 (1986). Writers Geoff Johns and Dave Gibbons incorporated several ideas from Moore's stories into "Sinestro Corps War", including the prophecy of the Blackest Night, Sodam Yat, Ranx the Sentient City and the Children of the White Lobe. Leezle Pon, a minor character only mentioned once in Moore's Mogo Doesn't Socialize story from 25 years previous, also makes an appearance in Green Lantern #25.
Work began on "Sinestro Corps War" in September 2006. The structure was fluid, at one point becoming a few issues with two bookends to just one gigantic issue. The title was originally just "Sinestro Corps", but during development the creators added the word "War". Eventually the structure finalized into a one-shot special for release in June, after which the story would alternate between Green Lantern and Green Lantern Corps until November. After the crossover's initial publishing successes, DC added four "Tales of the Sinestro Corps" one-shots to the publishing schedule.
Johns and Ethan Van Sciver first announced the crossover during the DC "Big Guns" panel at the 2006 Fan Expo Canada, with Johns calling it "the next level of Rebirth". By January 2007, Johns, Gibbons and editor Peter Tomasi had planned out most of the storyline. Sterling Gates, whom Johns had met at a convention, was brought in to write a backup story for the Superman-Prime one-shot and co-write Green Lantern/Sinestro Corps Secret Files #1.
The creators called "Sinestro Corps War" "World War II with the entire universe". In a September 2007 interview, Johns compared "Sinestro Corps War" to the Star Wars trilogy, with Green Lantern: Rebirth as A New Hope and "Sinestro Corps War" as The Empire Strikes Back. References to other science fiction stories were made by artist Ivan Reis, who inserted characters such as E.T., ALF and a Predator into large two-page illustrations. The writers also included the sound "EPA" in Green Lantern #25 as a direct reference to a scene in The Simpsons Movie where Comic Book Guy uses the sound while talking about a fight between Green Lantern and Sinestro.
There was much internal discussion at DC about how the storyline would be collected. Eventually DC decided to release two hardcover volumes (a February 2008 release containing the first five parts of the story and a June 2008 release containing the last six issues) and a June 2008 hardcover collecting the tie-in issues and backstories. This follows DC Comics' recent trend of releasing durable hardcover collections initially, followed later by softcovers.
Some changes were also made to the heroes during the course of the storyline. The role of Ion passed from Kyle Rayner to Sodam Yat, making Yat the "strongest Green Lantern in the universe" as a result according to Johns. The Book of Oa was rewritten by the Guardians to institute 10 new laws for the Green Lantern Corps, the first of which authorized lethal force against the Sinestro Corps. The rebirth of Coast City, the process of which had been seen throughout Geoff Johns' run on Green Lantern, as "the City Without Fear" was used to symbolically represent Hal Jordan's journey towards acceptance after his resurrection. The second volume of the story's collection revealed that the original plan was for both John Stewart and Guy Gardner to be possessed by Parallex, with artwork of them facing off against Hal Jordan. However, in the midst of the story planning, Johns realized this would make Parallex's possession of Kyle less effective and the segment was dropped and redrawn.
Green Lantern #25 expanded on the "emotional spectrum" concept and introduced five new color-based corps of similar structure to the Green Lanterns and the Sinestro Corps. These corps each draw from different emotions, corresponding with the seven colors of the rainbow (red for hate, orange for avarice, yellow for fear, green for willpower, blue for hope, indigo for compassion and violet for love). Ganthet and Sayd, two Guardians of the Universe who were exiled during the course of the war, were shown as developing the corps that corresponds to the color blue and the emotion hope, while the Anti-Monitor becomes the power source for an eighth color-based corps, the "Black Lanterns", who represent death and the "absence of human drives and emotions". The issue also laid the foundations for the 2009 event The Blackest Night, something the creators had been working towards since early 2007.
Critical reception to "Sinestro Corps War" was highly positive. IGN.com called the story a "smash hit" and Newsarama referred to it as both an "action-packed DC adventure" and "DC's blockbuster event of the year". Comic Book Resources released an editorial in mid-October 2007 entitled "Sinestro Corps War" is what World War Hulk SHOULD be", citing the former's ability to keep up and gain momentum throughout despite being both twice as large and far less publicized than the latter. Comic Book Resources placed "Sinestro Corps War" on its "Best of 2007" list, and named Geoff Johns one of its "Best Writers of 2007". In 2008, Ethan Van Sciver earned an Eisner Award nomination for his art in Green Lantern: Sinestro Corps Special #1.
DC Comics Executive Editor Dan DiDio praised the storyline as "the best thing that [DC Comics] put out this year. Without a doubt", and called "Sinestro Corps War" the model for crossovers in 2008 and beyond, including Final Crisis. Didio has also stated that he would like to see a direct-to-video animated "Sinestro Corps War" film similar to Justice League: The New Frontier. Geoff Johns suggested elements of "Sinestro Corps War" will appear in DC Universe Online, on which he is collaborating with artist Jim Lee.