The Battle began when Erik Selvig, under the control of Loki Laufeyson, used the Tesseract to open a wormhole above Stark Tower. The freshly arrived Iron Man attempted to deactivate the machine with a repulse blast that knocked Selvig unconscious, but he was unable to penetrate the energy field surrounding the generator. Stark then confronted Loki as a fleet of Chitauri warriors entered Earth's atmosphere through the wormhole from a distant region of deep space.
The extraterrestrials met initial resistance from Stark, but succeeded in wreaking destruction through the streets of New York City. Loki was next confronted by his own adoptive brother Thor, and the two fought on the catwalk atop Stark Tower at the same time that S.H.I.E.L.D. agents Clint Barton, Natasha Romanoff, and Steve Rogers arrived in a Quinjet to provide Iron Man with air-support. The Quinjet was shot down by Loki when it approached Stark Tower, but Barton managed to safely crash-land the jet; the three agents deboarded to discover the first of the Leviathans crossing through the wormhole and dispatching hundreds more Chitauri soldiers into the fight.
In the midst of the battle, Thor appealed to Loki to end the invasion, but Loki insisted that it was "too late to stop it" before stabbing Thor and leaping onto a passing Chitauri air chariot. Barton and Romanoff engaged Chitauri on the ground in a firefight while evacuating civilians, while Rogers ordered members of the New York City Police Department to establish a perimeter and begin moving citizens out of the surrounding buildings through basements or subways in order to "keep them off the streets." Rogers then rejoined Barton and Romanoff as Thor arrived to disable the battalion of Chitauri attacking them, and Bruce Banner reached the four moments later on a Triumph Bonneville.
Upon learning of Banner's arrival, Stark lured a Leviathan toward the team, and Banner transformed into the Hulk, single-handedly stopping the creature so that Stark could destroy it with a missile. As more Leviathans poured through the wormhole, Thor used the Chrysler Building as a lightning rod to discharge a massive blast of electricity into the wormhole, destroying several Leviathans and Chitauri. Barton took up sentry on a rooftop and Stark continued to engage Chitauri air chariots through the streets and buildings of the City. The Hulk launched himself into the battle, killing dozens of Chitauri warriors before single-handedly attacking a Leviathan.
Romanoff and Rogers continued fighting ground forces until Romanoff leapt onto a passing air chariot, disabling its riders and taking control of the vehicle. At the same time, Stark came to the aid of Rogers on the street before resuming his aerial patrol, and Thor joined Hulk in his assault on the Leviathan, which they managed to crash into Grand Central Terminal.
Soon after, the Army arrived to provide backup to the Avengers, and Selvig recovered from Stark's initial assault on the Tesseract device, the blast having freed him of Loki's control. Barton then directed Rogers to "a bank on 42nd past Madison" where Chitauri had "cornered a lot of civilians, and Rogers disabled several of the soldiers before one of their own grenades detonated, killing the rest of the hostiles without harming the civilians.
Using her air chariot, Romanoff lured Loki within Barton's range, and Barton fired an arrow that Loki caught in flight; the arrow was tipped with an explosive, however, and detonated, causing Loki to crash on the catwalk of Stark Tower once more. Romanoff also abandoned her vehicle, leaping onto the roof of Stark Tower as the Hulk arrived, attacking Loki inside the building and beating him into submission. Stark attacked a Leviathan by flying into its gullet and deploying dozens of explosives, but the detonation caused him to crash on the street where he was besieged by Chitauri fighters; Barton's vantage was overrun, causing him to abandon his post, and the Hulk was eventually surrounded by Chitauri air chariots who pinned him down with a barrage of fire.
The Avengers battled the invasion, keeping it confined to the area surrounding Stark Tower until the World Security Council authorized S.H.I.E.L.D. to fire a nuclear warhead into New York City. Nick Fury refused the order, but a fighter jet took off from the Helicarrier and launched a single missile toward the city. Fury warned Stark of the incoming warhead, and Stark took off to intercept the missile as Thor and Rogers continued the ground battle.
On the roof, Selvig explained to Romanoff that Loki's sceptre could disable the Tesseract's power source, and Romanoff used the sceptre to pierce the generator's energy field. Stark instructed her not to close the wormhole, however, and managed to directed the nuclear warhead through the portal and into deep space, where it impacted a Chitauri base ship. The detonation severed communications with the Chitauri fighters on Earth, disabling them in the streets of New York.
The Battle ended when Romanoff used Loki's sceptre to pierce the energy field around the wormhole generator and disable the Tesseract, sealing the wormhole only moments after Stark tumbled back through into Earth's atmosphere, where he was caught in mid-fall by the Hulk, who took the brunt of the impact as the two landed. Initially believed to be dead, Stark regained consciousness when the Hulk bellowed at him.
Following the Battle, Loki was taken into custody by the Avengers, who recovered the Tesseract and turned it and Loki over to Thor so that they could be safely returned to Asgard. The World Security Council questioned the decision, but did nothing to stop it. The public reacted to the Avengers with equal measures of adoration and skepticism, with Senator Boynton insisting that the heroes should be held accountable for the destruction that occurred throughout New York City.
- The Dark World (mentioned)