> Don't ya think we would have already located some extraterrestrials if there were wars going on in space?
Why would you think that? Let's open with a quote from Douglas Adams:
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”
Douglas Adams, The Hitchhiker's Guide to the Galaxy
Our own galaxy is 200,000 LIGHT YEARS across. This means it takes light 200,000 years to cross from one side to the other. It's friggin' enormous. And what we can observe is only relatively large energy sources like stars. Let's presume for a minute that there are some ETs happily engaged in armed conflict with each other 500 light years from us, tossing around 20 megaton nukes all day long like they're NBA players at a strip club making it rain. Assume that they are using 10,000 of such warheads against each others ships every day engaged in action around a star system. That's a total energy output of 200 GT (Gigatons) per day. The STAR in that system if it's a star like Sol will be putting out 7890000000000 GT per day of energy. How are we even supposed to detect 200GT more on top of that load? That's like going into Giants stadium at night and staring at the light arrays from the pitchers mound and trying to pick out someone flicking a lighter for a half a second in the midst of one of the arrays.
Secondly, I mentioned the "space is big" thing, right? Suppose these races developed doomsday devices that could actually kill stars and are happily wiping out each others' systems with nova-bombs. But they're fighting 500 LY away from us and their war only got really going 200 years ago. It's still going to be 300 years before we start seeing evidence of their handiwork.