A referendum on territorial status was held in the Territory of the Saar Basin on 13 January 1935. Over 90% voters opted for reunification with Germany, with 9% voting for the status quo as a League of Nations mandate territory and less than 0.5% opting for unification with France.
After the end of World War I, the Saar territory was separated from Germany and administered by the League of Nations. During this time, France was given control of the Saar's coal mines. After 15 years of League of Nations administration, a referendum was scheduled to take place in the territory.
Towards the end of 1934, the League of Nations Council determined that peacekeeping force would be necessary during the plebiscite period. The German and French governments agreed to allow an international force to enter the Saar, although Germany massed troops at the border. On 8 December 1934, the council unanimously approved a resolution calling for such a force. Britain (1500 troops), Italy (1300), Sweden (260) and the Netherlands (250) agreed to provide troops for the 3300-strong "International Force in the Saar". All expenses above and beyond those normally incurred for the same troops, were charged to the League fund set aside for the plebiscite. This may be "the first true example of an international peace observation force". The League appointed a commander, General John Brind, with operational control of the entire force. Troops patrolled, but did not police, the Saar. They were not to respond except to emergencies and at the request of local authorities. There was little or no violence during the plebiscite and the peacekeeping effort was regarded as a success.
While all important political groups in the Saar supported the Saar's return to Germany before Adolf Hitler and the Nazis came to power, opponents of Nazism in the Saar began having doubts and misgivings about a return of the Saar to Germany after Hitler's rise to power. Due to Hitler's oppression of their German counterparts, Communists and socialists in the Saar supported a continuation of the League of Nations administration and a delay in the plebiscite until after the Nazis were no longer in power in Germany. Meanwhile, Roman Catholics in the Saar were divided in regards to returning to German rule. In order to achieve victory in this referendum, the Nazis resorted to "a mixture of cajolery and brutal pressure". In 1933, Sarah Wambaugh, one of the members of the Plebiscite Commission, stated that complaints of a Nazi "reign of terror" were made by non-Nazi Saarlanders and by the foreign press. These complaints included allegations that the Nazis engaged in intimidation, "espionage, secret denunciations, kidnappings ..., ... interception of letters and telegrams, [and] listening-in to telephone conversations", among other things. In response to all of this, the Saar Governing Commission had to "promugulat[e] several restrictive decrees for the maintenance of public order". In November 1934, fearing armed intervention by France, the Nazi German government reduced its belligerency and changed its tactics. As a part of this, Joseph Burckel, Hitler's commissioner for the Saar, banned the wearing of uniforms within a 25-mile zone along the Saar frontier between 10 January 1935 and 10 February 1935. In addition, Burckel also banned meetings, parades, and processions in this area. Likewise, , the Nazi leader in the Saar, told his followers to obey the strictest discipline and implemented harsh penalties for any infractions.