Phil Klay’s “Redeployment” was a masterwork in mostly spare prose, its tonal range from laugh-out-loud, Joseph Heller-esque absurdity to soul-crushing bleakness. It may be our best literary window into the Iraq war.

A young Marine veteran’s literary debut, the short story collection won a 2014 National Book Award.

“Missionaries,” out Oct. 6 from Penguin Press, is Klay’s next act. A big, ambitious novel, it spans a few decades and continents and plumbs U.S. forever wars’ psychic imprint on peripatetic American warriors, militarism as a way of being and the consequences of ill-conceived foreign meddling.

Two U.S. Special Forces vets of Afghanistan and Iraq — transitioned to mercenary and a military attaché — have fought “in enough murky war zones to lack the near-religious faith in democracy that the war was sold on.” Their next stop is Colombia, where Washington’s targeting-killing apparatus, first turned on leftist insurgent, now hunts drug-trafficking warlords.

Colombia is a tremendously complex conflict. In fact, it’s not really one but a multitude of conflicts whose dizzying dynamics vary by region, a dirty war mostly of rural civilians suffering forgotten.

A callow U.S. journalist, done with Kabul, dispatches to Colombia, which she considers “an extension of the same war, not the endless war on ‘terror’ but something vaguer … related to the demands of America’s not-quite-empire which was always projecting military power across the globe and just shifting the rationale of why.”