«Patton's Spaceship» by John Barnes

First in the series blending alternate history, time travel, and detective thriller, from a Nebula and Hugo Award nominee.There are a million different Earths across an infinite number of timelines—and every one of them is in peril.Mark Strang became a bodyguard and private investigator when terrorists killed his family; now he spends his days protecting Pittsburgh’s helpless and abused. But while on a mission to save the life of a ten-year-old girl, Strang is inexplicably cast into an alternate reality, transported to a different time on another Earth, where America was defeated in the Second World War and now suffers under the brutal yoke of Nazi oppression. Joining up with the remnants of the Resistance in the Free Zone—and allied with such notable commanders as George Patton and John F. Kennedy—Strang is suddenly a marked man and the last hope in a desperate fight for freedom, not only on this world but on countless others. For a war unlike any other is raging across time and dimensions, threatening every possible Earth, including Strang’s own. And the enemy will not rest until the entire multiverse is in chains.In his epic and action-packed science fiction saga the Timeline Wars, John Barnes takes alternate-history SF to new heights, ingeniously reinventing and reinvigorating a genre popularized by such acclaimed authors as Harry Turtledove while joining the stellar ranks of Robert Heinlein and Joe Haldeman.