Born in Bremen, Forster attended the Schnepfenthal Salzmann School in Thuringia and the Altes Gymnasium in Bremen. He first worked as an actor, dramaturge and director at several southern German theatres. He was at the Meiningen Court Theatre from 1913 to 1917, and from 1933 to 1938 was acting director of the Bayerisches Staatsschauspiel and artistic director of the Bayerische Landesbühne in Munich. He was also a literary advisor to UFA.
After his acting days, he settled in Schlehdorf and devoted himself there only to dramatic poetry. He wrote stage-effective plays with historical but also contemporary themes as well as fairy tale plays, comedy plays and stories. He later returned to Bremen.
His best-known work is the play Robinson soll nicht sterben (1932). This play, which Gerhart Hauptmann praised as immortal, was performed many thousands of times. The novella of the same name dedicated to Gerhart Hauptmann (1942) was filmed in 1957 under the title The Girl and the Legend.
In 1933, Forster wrote a professionally calculated propaganda play for National Socialism with the political-heroic leader drama Alle gegen Einen, Einer für Alle, in which, against the historical background of the national Swedish uprising under Gustav I of Sweden in 1523, the Beer Hall Putsch of 1923 was brought to the stage. The play was performed over 300 times. The premiere took place on 21 February 1934 at the Theater des Volkes (Berlin), sponsored by the Nazi branch Kraft durch Freude. The manuscript was donated to the city of Munich, soon to be the "capital of the movement".
The play Der Sieger, which premiered in 1934, depicted the Saxons' struggle for freedom under Widukind. The antagonist was Charlemagne. Here, it was not only Germanism and Christianity that were in dispute, but primarily two political points of view. While Alfred Rosenberg argued for Widukind, Adolf Hitler stopped the debate. He saw Charlemagne as the representative of the Reich, which had priority for him. Henceforth, all Widukind plays were dropped.
Forster died in Bremen at the age of 62.
- Der Graue, 1917, Schülerdrama (Prize of the Volkstheater Vienna)
- Mammon, drama, 1918
- Madelaine und ihr Page Hyazint, 1919 Eigenbrödler Verlag
- Prinzessin Turandot, drama, 1923 (after a piece by Carlo Gozzi)
- Robinson soll nicht sterben!, drama, 1932
- Wendelin, 1932
- Matrosen in Würzburg, novella, 1932
- Alle gegen Einen, Einer für Alle, drama, 1933
- Der Sieger, drama, 1934
- Die Weiber von Redditz, comedy, 1934
- Die Verschwender, drama, 1939
- Gastspiel in Kopenhagen, 1940
- Ariela, 1941
- Robinson soll nicht sterben, novella, 1942
- Die Liebende, drama, 1945
- Die Gesteinigten, drama, 1946
- Candide, drama, 1948
- Ariel und die Schwestern, drama, 1949
- Bergkristall, Drama, 1954 (after Adalbert Stifter's eponymous story)
- Berlin Chronik
- The Stadttheater Lübeck not only performed the top plays Robinson soll nicht sterben (in Lübeck 1933) and Alle gegen Einen, Einer für Alle (in Lübeck 1933/34), but also Die Weiber von Redditz (in Lübeck 1936/37) and the aforementioned play Der Sieger (in Lübeck 1934/35), as well as the fairy tale play Der gestiefelte Kater (in Lübeck 1941/42 and again 1942/43). Cf. Jörg Fligge:"Schöne Lübecker Theaterwelt." Das Lübecker Stadttheater in den Jahren der NS-Diktatur. Lübeck: Schmidt-Römhild, 2018. ISBN 978-3-7950-5244-7. p. 565 235f.