Ts27se: I don't see any problem with it. Everything can be sensitive to a specific group of people anyways. And I mean, we already have stamps of generals, emperors, or controversial people/days from other countries, including Columbus Day. So what's wrong with having a stamp on one of the largest Vietnamese holidays?

It's not about boasting about war, it's about commemorating the tragic war that happened and celebrating the positive changes that come after!