I'm sure that "addClass" is working in that it's adding the class to the element, if (as @Gaby notes) you're doing it at the right time. Since it works in Firefox, you probably are.
Make sure the code runs after the DOM is loaded using.
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.