The best battle simulator.

There have been a number of battle simulators made for The Settlers Online, but my personal favourite has to be http://www.settlersonlinetools.com/en/combat_simulator/

It's the best looking by far, and even allows you to see the easiest way to defeat each camp. Camp selection is easy, and map based, rather than in the list style I've seen on some other battle simulators, which can get confusing.

A combat indicator is going to be integrated into the game at some point...but for now, bookmark this, and stop losing troops ;)