What rule did Germany break of the Treaty of Versailles?

Germany broke several provisions of the Treaty of Versailles, but one of the most significant was the reoccupation of the Rhineland in 1936. The treaty had established the Rhineland as a demilitarized zone to serve as a buffer between Germany and France. By sending troops into this area, Germany violated the treaty's terms, undermining the post-World War I peace and escalating tensions in Europe. This action was a key step in Adolf Hitler's broader strategy of reasserting German power and territorial expansion.