Conquistadors - Christopher G. Nuttall

The Protectorate—an interdimensional empire that has conquered five timelines so far—has set its sights on ours. Led by a man willing to risk everything for power and conquest, armed with technology a hundred years ahead of ours—technology promising salvation to its allies and doom to its enemies—and drawing on a far deeper military history, the Protectorate Expeditionary Force has arrived to invade and incorporate our world into the greatest empire the multiverse has ever known, or die trying.