In Canada, it happens all the time. We have one Force, but, 3 elements. A "purple" trade is not aligned to a particular element, despite the uniform that you wear.
E.g. , a cook can go from a Brigade Headquarters and Signals squadron to a ship, followed by an air base. It's no big deal at all.
I was in Communications, and did all three. When I joined, there was a Vietnam Vet of the US military who came back to Canada and joined the Canadian Forces. Joining the military in different countries is a lot more rare.
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.