As Schalk points out, the DefaultStyleKeyProperty identifies the key to the default Style, which must be contained in a Resource dictionary under a Themes folder. So if you move/rename your CustomTabItem. Xaml to be under Themes\Generic.
Xaml, then it should load and be applied.
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.