The game engine favours Player one.

[jmcarthur]

The rationale for the three-way battles is that each force sends one unit to combat at a time, and all units in combat at a time (one from each force) cancel out. So for example, if player A has 5 ships, player B has 3 ships, and neutral has 2 ships, the combat groups are ABN, ABN, and AB, which each cancel out, and player A has two ships remaining.

[katebus]

thanks jmacarthur, finally I was able to understand this ;-D

And tired of thinking about my bot ai, I made this ilustration (where 3 star ships are anihilating each other):