Not so much die as suffer a failure.
Shakturi come along, 'We are peaceful!' (yeah, right) I decide to attack them, my military was 8 times more powerful than theirs.
They repelled about half of my fleet and all of my invading ground troops. I sued for peace.
Building up my fleet. They appear to have reached a maximum on their fleet size.
Distant worlds with return of the shakturi and legends
I blew them up with a planetbuster the last time I saw them in my game. There was still an epic fight beforehand with me losing mid-late game capital ship in droves though.
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I turned my entire squadron right into some Japanese torpedoes and got to find out how much resistance Cleveland and Omaha-class light cruisers have against them. Complacency kills.
Fighting Steel w/ FSP 10.43, somehow got it to work on my computer.
I'd have grabbed the world destroyer, but there was only one, and another empire had started work on it.
Well, if that empire is friendly, and the World Destroyer is in an unaligned system or you have military access from them, you can post your fleet nearby and they may automatically takeover that death star once it finishes.
I know that because I had that happen to me once, but that's with the original DW at version 1.04 years ago, and things might have changed since then.
I was thinking your fleet was aircraft or small spacecraft or something. And you used them to "torpedo" enemy ships by running into them at high speeds carrying large quantities of explosives/fuel.
I should have used another word like flotilla or steer or something. My bad.