Most of the pictures were taken somewhere along the street Nowy Świat, in between Muzeum Narodowe and nearby Rynek Starego Miasta. There are many churches in this region, and they are certainly worth visiting. Many pictures were taken inside the Muzeum Narodowe and inside Muzeum Fryderyka Chopina. For more see here.
"Negotiations between Hitler and the British and French Prime Ministers, Neville Chamberlain and Edouard Daladier, resulted in the infamous Munich Agreement (September 1938), which allowed the annexation of Sudetenland to Germany. The Allies did not respond either to Hitler's invasion of Czechoslovakia on 15 March 1939 or to Mussolini's invasion of Albania on 7 April... The partition of Poland had been prepared in August, when the German and Soviet Foreign Ministers, Joachim von Ribbentrop and Vyacheslav Molotov, signed a non-aggression pact... Stalin's opportunistic collaboration [with Hitler] was underlined in the Red Army's simultaneous attack on Finland. The Soviet invasion of Lithuania, Estonia and Latvia followed in June 1940. This coincided with the crushing force of German Blitzkrieg in the west. In April [it] swept through Denmark and invaded Norway, where they met their first serious resistance. In May they pushed through the Netherlands, Belgium and Luxembourg; they entered France on 10 May..."