This one shot was part of the “Our Worlds At War” cross over event. The timing of this epic tale of Earth being devastated by an alien invasion and cities being levelled was unfortunate, as it was published around the time of the events of 9/11.
J’onn J’onzz is floating in space battered from battle calling telepathically to Superman for help. Green Lantern tells the rest of the Justice League that Martian Manhunter is down and their telepathic link may not hold. He uses his power ring to send missiles toward an enemy, while the Flash helps them along, claiming that although the alien alliance has suffered a setback, “the Justice League is the best line of defence for Earth!” He is soon, however, zapped by an Imperiex probe along with Plastic Man. As Imperiex continues to attack the League, Aquaman and Wonder Woman fight on, despite their fallen colleagues. They wonder where Batman and Superman could possibly be, and Imperiex taunts them, saying they are both dead and it will be Superman’s fault for the demolition of the galaxy.
On Earth, in Gotham City, Batman is having trouble keeping contact with Oracle, who does manage to relay the message that besides Gotham, Topeka, Kansas, has also been hit. Batman asks her to round-up Nightwing, Robin, Batgirl, and even Huntress if she must. He also tells her to contact the Justice League and tell them that Gotham is his priority.
In Smallville, Kansas, Superman flies off to the aid of the League through an emergency signal warning of aftershocks in Kansas. He arrives in time to save Aquaman from a probe by ripping its hand off. He explains that although the armour is for energy containment, he cauterised it as he flew by so it would not explode. Wonder Woman, however, attacks the probe with her shield despite Superman’s warning, and it explodes, nearly killing her. Superman pleads that Wonder Woman is not dead, and he does hear a faint heartbeat. Aquaman reminds him that they need to get the rest of the League to safety, while Maxima and Starfire show up with their ship, offering to help. As Superman flies off with Wonder Woman in his arms to the Space Ark, they inform Aquaman that one of the probes hit Atlantis and he tells them that if Atlantis falls, then so will rest of the Earth. He makes his way to a transporter to leave. On the Space Ark, Superman brings Wonder Woman to Hippolyta, who left the Justice Society of America when she heard about her daughter, telling her that Wonder Woman needs her help.
At the White House, General Rock is informing President Luthor of all of the major cities that have been targeted by the probes, including Topeka, Krasnoyarsk, Frankfurt and Atlantis, however, Luthor already knows all of the information despite the fact that it just came in from N.O.R.A.D. Veridium, the robotic personality of Doc Magnus, explains that they have found new information on Imperiex. The Imperiex mind controls all of the probes as a hive-mind, and the cities that have been attacked are each at the dead centre of their continent. Luthor asks who Earth has left to defend itself, now that the Justice League is done. General Rock lists the Justice Society, the Titans and Young Justice, and Luthor calls for all of them.
In each of the cities, there are defenders for the Earth. In Krasnoyarsk, Russia, Blue Beetle’s team of himself, Booster Gold, and Guy Gardner are fighting a probe, who apparently kills Gardner. In Frankfurt, General Zod is defending, in Zaire the Titans are fighting, and the Outsiders are fighting a probe at the South Pole.
On the Space Ark, a bed-ridden Green Lantern asks Superman if they won. Superman tells him to get some rest while the Flash lies next to him in a similar condition. Lois appears and runs to give Superman a hug. While they share a private moment with her asking what happened, Maxima approaches, telling Superman that Atlantis is under attack and he is needed. He tells Lois he needs her to stay safe as he flies off to help.
In Atlantis, Aquaman says his goodbyes to Mera and Tempest, telling them to keep the city safe if he should fall. Aquaman then goes off to fight the probe himself. While attacking, he asks for Father Neptune to give him strength, and finally is able to give the final blow to the probe. This, however, causes an energy explosion and apparently kills Aquaman. Superman makes it to Atlantis in time to see the explosion, and realises that Aquaman is dead. His cry is mighty as it parts much of the sea, yelling “IMPERIEX! If you want war…I’ll give you WAR!”