It seems that an NPR had something to say that I landed troops on their homeworld but in my colony, no war, at the time...
After I placed several laser (STO) batteries they declared war... And promptly started nuking my batteries...
That and several more waves of missiles made a "nuclear winter", -64.44 Celsius from those missiles and energy bombardments...
Would be nice if NPRs don't start war with committing suicide...
Hmm, its on a world with Taiga... Some 28000 shots from my troops gives less than 200 hits/kills...