How to make a board game about the Battle for Iwo Jima?

I have a history project where I have to make a board game about the Battle for Iwo Jima. Does anyone have any idea on how I can go about doing this? I am very confused and don't know how to start. I need to emphasize the tactics made by the United States in it too. Please, if anyone out there is able to help me, I would greatly appreciate it.

Answer: 
Don't make your own, copy one of the existing Iwo Jima board games. See the links.