There are a handful of achievements, including hidden ones that involve killing 10, 50, and 200 troops with collateral damage.



From google and search here, this seems to be defined as when AI invades you with troops - kill X number of his troops as he takes your system (just like when I use troops to invade an AI system I can lose troops)



This would be lot easier if it counted the troops I lost, but apparently it only counts the troops of the AI you kill, which means only works if the AI invades you - which leads to my question --->



Q: How or what is a good way to get the AI to invade my systems?



*Obviously, I need to just sit back and not intercept with my fleets - but then what? And what defenses do I build or not build? I assume the 3 levels of the anti-aircraft defense building? (it seems only one of the buildings listed that notes on card that it causes +X collateral damage)



**note - this seems pretty tricky and hard achievement; the kill/fighter bomber ones including hidden ones that go up to 200 killed I am slowly getting just by playing the game and using fighters on my ships to shoot down AI fighters/bombers. But this kill troops by collateral damage seems pretty hard to trigger - I'm not having the AI use troops it seems, just invasion power (or bombs my planets but not troop invade - just bombs, then siege invades)