Imperium — a series by Lumpy

An Uncertain Future in a New Past. During the test flight of a prototype faster-than-light craft, Lt. Commander Ky is flung into the ancient past that never existed. Rome has fallen, defeated by the mighty Carthaginian Empire. Hounded by the Carthaginians bent on conquering the known world, Rome is on the verge of destruction. Stranded and alone, except for a tactical AI implanted in his head, Ky has lost everything and must find a way to live in a world different than anything he's ever known.

The Carthaginians are marching to destroy Rome and it is up to Ky, a test pilot from the future thrown into an alternate past, to keep the once mighty Roman Empire from being destroyed. As Ky gathers Roman and Caledonian forces together to form a new Britannic Empire to defend against the Carthaginian host, he must also struggle to contend with a malfunctioning AI implanted in his brain that is slowly gaining sentience. Thankfully, Ky is not alone.