Operation Himmler
From Wiki. Take the accuracy for what it's worth.

Operation Himmler was a Nazi Germany false flag project to create the appearance of Polish aggression against Germany, which was subsequently used to justify the invasion of Poland.

The operations, with one exception, were carried on the 31 August. There were 21 separate operations, including staged attacks on:

  • the German radio station Sender Gleiwitz (Gliwice) (see Gleiwitz incident)
  • the German customs station at Hochlinden (today part of Rybnik)
  • the forest service station in Pitschen (Byczyna)
Convicts from concentration camps were killed and left dressed in Polish uniforms (dubbed the "Konserve" i.e., canned goods).

On 1 September, in a speech in the Reichstag, Adolf Hitler cited the 21 border incidents, with three of them called very serious, as justification for Germany's "defensive" action against Poland. Just few days earlier, on 22 August, he told his generals "I will provide a propagandistic casus belli. Its credibility doesn't matter. The victor will not be asked whether he told the truth."