I wager your tilemap is simply too big. On the simulator it doesn't matter that much since the Simulator makes use of your Mac's memory, which is probably anywhere between 2 to 16 GB. The largest iPad can offer is 1 GB, and earlier devices only have between 128 to 512 MB.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.