The Locarno Treaties were seven agreements negotiated in Locarno, Switzerland, from 5 to 16 October 1925 and formally signed in London on 1 December, in which the First World War Western European Allied powers and the new states of Central and Eastern Europe sought to secure the post-war territorial settlement, in return for normalizing relations with the defeated German Reich. It also stated that Germany would never go to war with the other countries. Locarno divided borders in Europe into two categories: western, which were guaranteed by the Locarno Treaties, and eastern borders of Germany with Poland, which were open for revision.

The Polish Corridor, also known as the Danzig Corridor, Corridor to the Sea or Gdańsk Corridor, was a territory located in the region of Pomerelia, which provided the Second Republic of Poland (1920–1939) with access to the Baltic Sea, thus dividing the bulk of Weimar Germany from the province of East Prussia. At its narrowest point, the Polish territory was just 30 km wide. The Free City of Danzig, situated to the east of the corridor, was a semi-independent German speaking city-state forming part of neither Germany nor Poland, though united with the latter through an imposed union covering customs, mail, foreign policy, railways as well as defence.