An ongoing timeline/crossover written by Gaius_Julius_Magnus in which The Race from Harry Turtledove's Worldwar series invading the world of Tl-191, otherwise known as Southern Victory and focuses on the characters from that world in their fight against the Race invasion. Besides from the Race, human characters from Worldwar make appearances as well. It's also a redo of a previous story done by GJM back in 2012.
It can be read Here. A story only version will be posted when it is complete.
In addition to the characters from the two aforementioned series, other characters from Harry Turtledove works make appearances.
The War That Came Early
Days of Infamy/End of the Beginning