In the summer of 1923, Germany found itself in the grip of an intense revolutionary ferment. But this historic opportunity for the working class to seize power was squandered, with devastating implications, not only for Germany, but for the course of the world socialist revolution. In this article, marking the hundredth anniversary of the dramatic failure of the German Revolution in October 1923, Tatjana Pinetzki explains how this situation emerged, the mistakes of the leadership, and the impact of these events on world history.