Plenty of this type although only tbs one I know is castle wars and that is more of a card game.
What system would the game be meant for? Computer, mobilePC? iPhone?
Consider what resolution you'd want the game at.
Members in forum chat could suggest what resolution is best for what ever system your game will be on.
Refine your game design ideas and rules.
Figure out how people would play it and how it would look to them.
Then you can start gathering pieces to make a prototype game.
A background picture to fit the resolution.
It doesn't have to be fancy. Should just use place holder pictures to start.
Get a picture to represent your soldiers. Can be simple stick person like my example shows.
A picture for your castles/bases.
And you should have the first building blocks for your game ready to put into GE then. =)
Do some of GE's tutorials on how it works.
Once you can get some normal actors for Background,soldier, castle1 and 2. Come back for w/e info you need on turning your actors into your pictures and making them do w/e is needed. =)
Hope this helps get started.
Once again many game editor site/forum tutorials can be applied to the things your game will need to get started.