it breaks every law in the book including Nuremberg and the constitution
I don't doubt your experience, however it seems strange in a country with thousands of very litigious lawyers and an assertive democratic structure that such a situation can occur.
Stalin was getting ready to invade as well. Hitler just beat him to it.
In cahoots, however Hitler got there first.
And of course, wars start slowly. The invasion of Poland was the straw that broke the camel's back. Military action started before that If anything, the war started with the invasion of the Sudetenland if not the Rheinland.
Different countries date things differently. In Poland, it was September 1939 to May 1945. For Brits, September 1939 to August 1945. For Yanks and Japs, 1940 to August 45. A Russian would say their own dates, from Barbarossa to Berlin and the Chinese would say the war started when Japan invaded in the 30s.