I changed the planets owner to militia1 then added a group and added a few ships to the group , and did the same for the rest of the planets , now when I load the game the first time the militia do spawn and its nice and hard but when I reload the map again the militia do not spawn and I am not sure why this keeps happening , can any one perhaps help me with that ?
Use RandomMilitia instead of militia1. I don't know where you found the advice to use militia1, but it would have worked a long time ago for trinity and earlier maps. What happened is that there are twenty or so militia players that can randomly be assigned to unowned planets on the map. Before Rebellion all twenty of these players were loaded, so you could always use their specific number as well as RandomMilitia to get them to spawn. However, Rebellion decided to save memory space by randomly picking five militias to load each game, and all neutral ships will be assigned to one of these random five instead of the random twenty. If militia1 happens to be one of the randomly selected the map will work, if it is not those ships will not spawn.
Again, the solution is to use "RandomMilitia", which will use any of the loaded militia players, so you can be sure it will always works (indeed its what the game uses for the default forces). You can also use a handful of other players who are permanently loaded, including "Pirate" and "Rebel".
on a other hand since I am pretty new to sins I tough I should ask what race some of you use and for what reason you use that race , just so cna get a better understanding how that works other then having different ships and such .
Advent Rebels are my favorite, Advent was my favorite before Rebellion and bringing back enemies to fight for you gave them this weird holy necromancer feel I like. Also while some might argue that its not the very best, the Eradica titan is a beast and any experienced Sins player will know not to challenge its wrath once its level 6, or to be ready to run at a moments notice while doing so.