The populist tide nevertheless proved unstoppable: in January 1933 the Nazi Party took power and lost no time in transforming Germany into an unconstrained one-party dictatorship. Directly following the Reichstag fire at the end of February 1933, Chancellor Hitler's government blamed "communists" and launched a major round-up of those who had been active Communist politicians before the regime change. Johanna Ludewig fled, initially to Britain and then to Denmark. However, she returned to Germany in 1934 and took a job as a book keeper in Berlin. She was kept under police surveillance and on several occasions interviewed by the Gestapo. According to one source she was arrested in 1937, but there is no indication of any lengthy period of detention at this point. However, in 1944 the unsuccessful assassination attempt against Hitler opened the way for a massive further round-up of people still in Germany who had been politically active as communists or socialists before 1933. Johanna Ludewig was arrested, like several thousand others, towards the end of August 1944 in connection with what came to be known as Aktion Gitter. She was taken to the Ravensbrück concentration camp. Approximately three weeks later, on 12 September 1944 she was released, but after this she spent several more weeks in police jails in Berlin.