I've added and changed a couple of my older hubs - perhaps new photographs or adding new information. This is a great feature of Hub Pages I think, rather than having to delete a hub and then a full re-write. This is a really good question for new hubbers who, like myself when I first started, didn't know things such as editing old hubs and so on.
You can always go back and edit your hubs to fix mistakes or add completely new sections. If you are adding a substantial amount of new material it may be better to just make a new hub and link the two together.
I like to add updates -- about a paragraph of new material -- to my older hubs. I notice that doing this usually raises the hub's score. Adding relevant, new material can result in a stronger hub.
Linking hubs as junkseller suggests is a good strategy. I'm just getting back into HP myself. Good luck!
You can add to your original hubs all you want.
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.