So I dropped 2 brigades of troops onto an alien colony, where I out-massed their ground force tonnage 2:1 and......my troops got their butts kicked. Turns out the alien infantry had armor penetration that cut right through my power armor design. So I loaded my survivors (<50%) back into the transports which bugged out to my nearest Fleet Base and awaited new ground unit and formation designs for a second attempt. Meanwhile, I sent some of my Fleets to other nearby systems, but kept about a dozen vessels in orbit (previously, this system had been the site of a major battle so the bulk of my Navy was hanging around with Orbital Fire Support orders).
Eventually, I guess the aliens decided to attack and destroy my "pop" of 0 people on their world.......when that happened, I "lost" 0 wealth........but my entire fleet in orbit surrendered to the enemy!
I couldn't figure out how to undo that in SpaceMaster mode so I just loaded my previous save, which was fortunately yesterday and without significant changes since. That seemed like a completely ridiculous result to me. Be careful out there, Space Admirals! (I'm on v1.9.4? 5?, so dunno if this was changed in v1.10).