As Marvel Comics moves to its next major crossover event in Empyre, the upcoming storyline offers a twist on the classic Kree-Skrull War that has engulfed the cosmic side of the Marvel Universe for decades: The two warring empires will join forces in a new interstellar alliance to invade the Earth under the leadership of the alliance's new emperor, Hulkling. Earth's heroes are accustomed to uniting against a common enemy but, instead of being caught in the middle of extraterrestrial belligerents, the Avengers and Fantastic Four's history with the Skrulls and Kree will work against them in the coming crossover.
Both the Skrulls and Kree were created by Stan Lee and Jack Kirby in the pages of Fantastic Four, with the former appearing as the main antagonists in 1962's issue #2 and the latter debuting in 1967's issue #65. The shared history between the Skrulls and Kree was later revealed, with the Skrulls observing the savage, humanoid Kree and the sentient, plant-based Cotati. The jealous Kree nearly wiped out the Cotati entirely before attacking the Skrulls and stealing their technology to become an advanced, spacefaring race, with the two empires battling across the cosmos.
This first came to a head in the 1971 storyline "The Kree-Skrull War" running through Avengers #89-97. Written by Roy Thomas and illustrated by Sal Buscema, Neal Adams, and John Buscema, the epic storyline had Earth caught in the crossfire of the escalating conflict after the Kree hero Mar-Vell returns weakened to the Earth. The Avengers eventually discover that the Kree's religious warrior Ronan the Accuser intends to devolve Earth's population and use the planet as a future staging ground for the Kree to carry out its ongoing conflict against the Skrulls.
After Ronan is defeated, the Avengers are confronted by the shape-shifting Skrulls, revealed to be part of the initial expeditionary force defeated by the Fantastic Four during their first appearance. Three of the initial group of four Skrulls are exposed and defeated while the fourth remains hidden amongst the humans. Meanwhile, U.S. Senator Craddock has taken a hard-line stance against the Avengers, helping turn the general public against Earth's Mightiest Heroes.
After the Avengers stop a second Kree force that helped install Maximus as the head of the Inhumans and restore Black Bolt to the throne, they are briefly captured before being freed by Mar-Vell and Rick Jones and repel a Skrull armada and force a truce. Back on Earth, Craddock himself is revealed to be the hidden fourth Skrull and killed by an angry mob -- thus restoring the Avengers' reputation.
Years later, it was revealed that while Mar-Vell was held captive by the Skrull Empire, the Kree warrior fell in love with the Skrull Princess Anelle and the two conceived a child in secret. The child would grow up to become the Young Avenger Hulkling, an heir to both the Skrull and Kree thrones due to his mixed heritage. The two empires nearly restarted their war on Earth over Hulkling before the planet's superheroes made them stand down. Hulkling later accepted his regal destiny, forging an alliance between the two races while taking the throne as the alliance's joint emperor.
"The Kree-Skrull War" was one of the Avengers' most pivotal storylines and one of the first longer-form stories told across nearly 10 single issues. The incident helped inspire the creation of the Illuminati, uniting key figures from across the Marvel Universe to proactively address threats from the shadows. But now, united against the heroes of Earth, the Skrulls and Kree appear to have the upper-hand with Hulkling at the helm.
Written by Robbie Thompson and illustrated by Mattia De Iulis, Javier Rodríguez and Álvaro López, Road to Empyre: The Kree/Skrull War #1 is on sale now from Marvel Comics.