In 1892 Cohn obtained his doctorate and served in the
Prussian Army in 1892/93. In 1897 he started to practise as a lawyer in Berlin and joined the law-office of
Karl and
Theodor Liebknecht in 1899; as a lawyer working in Berlin, Cohn also co-operated with
Wolfgang Heine. In 1909 he became a member of Berlin's city council for the
Tiergarten district for the Social Democratic Party of Germany (SPD). In 1912 Cohn was elected a member of the
German Reichstag representing
Nordhausen. In World War I Cohn served as a guard in
prisoner of war camps in
Alsace,
Guben,
Lithuania, and
Courland from April 1915 to June 1917; during this time he had his first significant contact with
Eastern European Jewry. Cohn was regularly exempted from military service to take part in Reichstag sessions. When news about the
Tel Aviv and Jaffa deportation reached Berlin, Cohn brought up the issue in the Reichstag on 7 May 1917. On 14 May he applied a parliamentary interpellation to intervene in the policy of
Djemal Pasha in Palestine. The deportations were finally stopped by
Erich von Falkenhayn. Cohn joined the
Independent Social Democratic Party of Germany (USPD) in 1917 and was a member of the USPD delegation at the
Stockholm Peace Conference of June 1917. Along with
Hugo Haase,
Karl Kautsky, and
Luise Zietz, he met
Angelica Balabanoff and the Russian delegation on 3 July 1917. Here in Stockholm he also came in contact with
Ber Borochov and the
Poale Zion movement. After the restoration of diplomatic relations between Germany and Russia, Cohn became legal advisor of the Russian delegation in Berlin. In early November 1918, the Russian delegation was expelled on charges of preparing a Communist uprising in Germany. On the night of 5 to 6 November,
Adolph Joffe, the Russian ambassador in Berlin, rendered him about 1 million
Mark and a 10.5 million
Russian ruble mandate for a bank account at
Mendelssohn & Co. After the delegation returned to Russia, Joffe claimed to have paid this money to the USPD to support the revolutionary activities and to purchase weapons. While the leading USPD politicians
Hugo Haase and
Emil Barth denied the payment, Cohn admitted the receipt and regretted that he was not able yet to spend the complete sum to spread the idea of the revolution. He explicitly denied receiving the money to acquire weapons; instead he had used most of the cash money to support employees of the embassy and Russian nationals in Germany. Because he could not use the bank account for formal reasons (the Mendelssohn bank refused the mandate), only 50,000 Mark were used to support a socialist uprising in Germany. Cohn also justified the receipt because the SPD had provided money to Russian socialists in the
1905 Russian Revolution in a similar way. He was however criticised, also by socialist newspapers like
Die Freiheit and
Vorwärts, because his actions stood in contrast to a USPD party resolution, which ruled out the acceptance of foreign money for revolutionary purposes. These payments led to the demission of
Wilhelm Solf as
German minister of foreign affairs, who refused further cooperation with the USPD. After the
November Revolution, Cohn became undersecretary in the
Reich Ministry of Justice. In January 1919, Cohn was elected a member of the Weimar National Assembly. His motions to replace the term "Reich" by "Republic" and to address German Jews as a national minority in the
Weimar Constitution were denied by the Assembly. In November 1919, Cohn became a member of the so-called "Schücking Commission", an official commission to investigate Allied allegations of illegal treatment of prisoners of war in Germany, named after its chairman
Walther Schücking. In the case of
Charles Fryatt, who had been executed by German authorities in 1916, Cohn and
Eduard Bernstein dissented from the commission's verdict and publicly declared that they regarded the execution as a severe infringement of international law and an "inexcusable judicial murder". From 1920 on, he represented
Poale Zion in the Jewish community of Berlin, especially advocating the equal status of eastern european Jewish immigrants. In 1922 Cohn re-joined the SPD; he left politics in 1924 and focused on religious affairs in Berlin. He continued to work as a lawyer in Berlin and became a member of the
German League for Human Rights. Cohn managed to escape from Berlin the day after the
Reichstag fire of February 1933. He moved to
Paris where he worked for the
Hebrew Immigrant Aid Society (HICEM). In August 1934, Cohn took part in a conference of the
World Jewish Congress in
Geneva. While in Switzerland, he was diagnosed with
lung cancer. He died in Geneva and was buried in
Degania Alef, a
kibbutz in northern Israel. The funeral orations were given by Zionists
Nahum Goldmann and
Yosef Sprinzak. ==Remembrance==