Two, with a third planned. Cascadia Fallen is the original trilogy. Blades of Grass is the large, world-war-themed spinoff. And a second spinoff called Conner's Mission will be releasing sometime in the 2023-2024 winter.
Any! I've written them independently. With books two and three of Cascadia Fallen, I'd introduced new characters, which caused some timeline jumping (as we learned how they dealt with the sudden disasters.)
Blades of Grass and Conner's Mission is (and will be) linear. There are a handful of crossover characters that help it all tie together, but you won't be missing anything to read Blades first. In fact, I'm putting out several in rapid order, so if you're a fast reader, that's probably the way to go.
When I wrote Tahoma's Hammer, I was still in a career at a naval shipyard. As I started writing, I realized I wanted the Phil Walker story out at the gun club to be the primary story. The shipyard plot was to pay tribute to all of my old colleagues. And even though it was not a major piece of book 2, that navy presence did come back for a very important moment in book 3! [And in Blades of Grass, too!]
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