Foerster was strongly opposed to the German foreign policy in the era of the First World War, particularly the militaristic attitudes of the ruling elite in Germany.

His criticism of the political legacy of Otto von Bismarck during the war caused a great scandal at his university, and he was dismissed from his post for two semesters.

When Foerster returned from Switzerland in 1917, he remained convinced that responsibility for the World War lay with the ruling elite in Germany, and particularly with the leaders of the military.

[1] His views made him highly unpopular with the conservative factions of German society and he became seen as a key enemy by the newly created national socialist movement.

In 1920 he published his book, Mein Kampf gegen das militaristische und nationalistische Deutschland (My struggle against the militaristic and nationalistic Germany).

At the book burning in Berlin on May 10, 1933, the prescribed "fire speech" consigned Foerster's writings to the flames with the words Gegen Gesinnungslumperei und politischen Verrat (Against immoral opportunism and political betrayal).