Dresden was the sanctuary for refugees from all of Germany, the only city not bombed into oblivion until then. It was an intentional trap, and 600.000 is a ridiculous number. I believe in the higher end estimates, that between 3-4 million women, children and wounded had been there.
Probably the biggest individual act of genocide in history. Only rivaled by the allied death camps, set up post war. Interesting theory though.