Require model field in admin site only if another model field is true?

You actually only need to override your model's clean method.

Create form for the ThingTwo and check what you need in model's clean() method.

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.