26 house 1926 r. Józef Piłsudski's supporters made an armed coup.

After 1930 r. the street layout was modernized (exit arteries were widened, Aleja Niepodległości and Żwirki i Wigury were marked out, new road viaducts were built, new squares were created, an airport in Okęcie was built). Numerous government and public buildings were erected. A number of monuments have been erected. Several parks were also established. W 1938 r. the first trial broadcasts of a television program were made. W 1939 r. the number of inhabitants was 1 357 000.

During the defensive war in September 1939 r. Warsaw was a place of fierce fighting. The first bombings have already taken place 1 September 1939 r. The besieged Warsaw was placed by 3 weeks of resistance to the Germans. The city's defense commander was Gen.. Valerian Czu-ma, and the city mayor, Stefan Starzyński, will be the civil commissar. The heroic defense of the city focused on its outskirts: m.in. in Rakowac, Bielany, will, Sadyba and in Marysin Wawerski. In October 1939 r. the first planned arrests of residents took place, especially representatives of the intelligentsia, scientists, social and political activists. 26 October 1939 r. the Nazis arrested the mayor of the city, Stefan Starzyński. In November 1939 r. higher and secondary schools were closed, many institutions and associations, newspaper editorial offices. Cards were introduced to provide the population with necessary articles. The first mass executions of the civilian population were carried out by the Nazis in December 1939 r. (Palmiry and Wawer). In November 1940 r. in Warsaw was created on an area of ​​over 300 ha ghetto for Jews, from where they were systematically taken to extermination camps (mainly Treblinka). There were numerous arrests during the Nazi occupation, round-ups, street executions and deportations to forced labor and extermination camps. Many works of art were destroyed or looted, cultural monuments, monuments and libraries. Eventually 1939 r. the first structures of the underground state and armed troops were created. First, the Service for Poland's Victory was established, w 1940 r. was transformed into the Union of Armed Struggle, a w 1942 r. into the Home Army. 5 January 1942 r. The Polish Workers' Party was established in Warsaw (PPR). From 19 April to 16 house 1943 r. the uprising in the ghetto continued, organized by the Jewish Combat Organization. In July 1944 r. approached Warsaw from the east. The Red Army and the units of the Polish 1st Army of the Polish Army cooperating with it. Soon, in September 1944 r., German troops were forced out of Prague. 1 of August 1944 r. on the order of the Home Army command, the Warsaw Uprising broke out.