Over the last six years, author Marko Kloos has forged an impressive career for himself with Frontlines, his popular, long-running military science fiction series. This year, he’s shifting gears, setting aside Frontlines to start a brand new series called The Palladium Wars, a space opera set in the aftermath of a devastating war.

Kloos’s series began its life as a submission to the Viable Paradise SF/F Writer’s Workshop — an annual boot camp on Martha’s Vineyard that pairs aspiring writers with seasoned professionals. He wove in his own experiences as a non-commissioned officer in the German military into the story, which followed a recruit named Andrew Greyson, who joins the military to escape from the slums of an overcrowded North American Commonwealth in 2108. Kloos later expanded those initial submission chapters into a complete novel, and self-published it on Amazon.

That self-published novel, Terms of Enlistment, took off, with readers comparing the book to Robert Heinlein’s Starship Troopers or John Scalzi’s Old Man’s War, and praising Kloos’s realistic approach to military life. Amazon eventually acquired the novel for its own in-house science fiction imprint, 47 North, which allowed Kloos to go on to write five sequels.

And that’s where the series ends — for now. Kloos’ next book isn’t a continuation of the series that defined his career, but is instead the start of a new space opera trilogy called The Palladium Wars. The first installment, Aftershocks, hits bookstores this July.

“The new series is going to be kind of Expanse-y,” Kloos tells The Verge. “Frontlines is straight-up military sci-fi, because the first-person protagonist is in the military. The new series [has] four different viewpoint characters and it’s third person, past-tense.”

A key element for Kloos was building a brand-new, six-planet star system called the Gaia System, as opposed to going the Expanse route by setting it in our more familiar solar system. “I wanted to free myself from the constraints of what you’d have if you worked with an established planetary system. With a new planetary system you made up yourself, you have freedom with the world,” he says.

An eye-opening moment for Kloos came when he attended another science fiction workshop: the Launch Pad Astronomy Workshop, held each year at the University of Wyoming in Laramie. (Disclaimer — I was an attendee in 2014). The week-long boot camp is engineered to impart science fiction writers with a baseline of astronomy and physics knowledge, with the idea that more scientifically accurate works will in turn help provide readers with better science. “That gave me a lot of ideas that I wanted to put into this series,” he says, “and basically created the solar system from scratch.”

The workshop “taught me all the things I did wrong with Frontlines, which was luckily not a whole lot,” Kloos says, “but there are some whoppers in there, like a colony around a star that does not support a habitable zone.” As he set about developing his new series, he incorporated what he learned in the workshop to develop his setting, which translated into a wealth of story opportunities.

That conflict grew out of how Kloos built his the system. In this story, palladium is a vital component in this world’s technology, chiefly for the production of artificial gravity generators. As one planet maintains a tight grip on the system’s resources, tensions with its neighbors grow to a breaking point, resulting in a war that kills tens of millions.

Aftershocks is set in the aftermath of that massive, system-wide conflict over resources — namely palladium — that saw its instigator, the planet Gretia, endure a major defeat and occupation by its enemies. One of the story’s central characters, Aden Robertson, was on the losing side, and he’s just been released from a POW camp where he’s had to contend with the atrocities that he witnessed during the war. Kloos explains that he wanted to deal with a character who had to come to terms with the collapse of a system he supported for two decades, and “how you find your identity after that.”

Kloos’s German roots also figure into the geopolitics of the series

Kloos’s own German roots figure into the larger geopolitics of the series. “I totally cribbed from history,” he says. “The aggressors here are basically space Germany. It’s kind of like this cross between the end of World War I and the end of World War II. I kind of mashed it up a bit so that there’s a set of circumstances where it was a war of aggression, and they definitely are the bad guys, but also make the war logically understandable and consistent — a war for resources.”

The new series will also allow him to explore new characters and a vastly different environment. Kloos says that he’s spent the last six years in protagonist Andrew Greyson’s head, writing from Frontlines’ first-person perspective. That requires a lot of juggling simply because that character has to see and recount everything, and as a result, Frontlines features a character that doesn’t have a lot of agency — his story is a small one in a much larger conflict. In contrast, Kloos says having four characters to jump around with means that he can tell a much bigger story, one in which his characters can meaningfully drive the story forward. “If I want to describe an event, I don’t have to figure out how to bring my character to it.” Kloos has big plans for the series, noting that while he’s only under contract for two novels, “I am planning Palladium Wars as a longer series because the world is just so much more layered and complex than Frontlines, but all will depend on how well fans take to it.”

The Palladium Wars isn’t the only thing on Kloos’s plate. He’s part of George R.R. Martin’s long-running Wildcards superhero series, with a story in last year’s installment, Low Chicago, and more on the way. And for Frontlines fans, he says that he’ll be returning to that world with a novella and novel, set to be released later this year and next, respectively.

The Palladium Wars: Aftershocks will be released on July 1st.