Category_id is not the first column in any index.
You are not using the index. When you have a composite index like (content_id, category_id) you can use the index by using content_id or you can use content_id and category_id. You can't use category_id and utilize the index.
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.