What is a good free RTS game creator to make a game like World War on Facebook

The best RTS game maker i know is Warcraft 3.Don't think it's only a RTS game, It has a world editor which you can make your own map but it doesn't only make maps for you , you can Download or Make your own units.I made my own WW2 game . Not only you can make RTS games. I managed to make a RPG game.It's not free but it's the best RTS creator.