(TWP: These are documents from the USSR, I have no idea whether they are real or fake)
Link in the Tweet:
September 30, 1938.
Letter from Foreign Minister of Poland Jozef Beck to Polish Ambassador to Czechoslovakia Kazimierz Papee, instructing him to deliver the ultimatum to the Czechoslovak Government.
As far back as July 16, 1938, French Ambassador in Warsaw Leon Noel openly asked Jozef Beck: “What prevents Poland from giving a written pledge not to attack Czechoslovakia?” Minister Beck replied: “This is like asking a gentleman to pledge in writing that he would not cheat at cards.”