Wokuo Incursion

Invasion from an alternate timeline?
It's December 1937 in a world exactly like ours except that it is about to veer wildly into alternate history. It's less than two years before World War II broke out historically in Europe. War has already come to much of Asia, with Japan invading China. An isolationist US fears it will be drawn into that conflict, especially after the Japanese sink the US gunboat Panay. Just when President Franklin Roosevelt thinks he has that crisis under control, he faces a bigger issue. High tech descendants of the Wokuo, Japanese pirates and smugglers who should have vanished over three hundred years ago, flood into the Pacific coast off California.

The Wokuo are both refugees and invaders, fleeing from war in an alternate reality where they survived and grew strong, while looking for new conquests to replace their lost empire. They set their sights on California. President Roosevelt sends disgraced former Colonel Martin to California to organize resistance to the invaders, but the Colonel has his own issues, buried deep in his brain and waiting to cause disaster.