Lithuania declared its independence from Russia in 1918 during World War I. Some Prussian Lithuanian activists signed the Act of Tilsit, demanding unification of Lithuania Minor and Lithuania Major into a single Lithuanian state, thus detaching the areas of East Prussia from Germany which were inhabited by Prussian Lithuanians. This claim was supported by the Lithuanian government. The part north of the Neman River up to Memel was separated from Germany by the Treaty of Versailles in 1920, and was called the Memel Territory. It was made a protectorate of the Entente States, in order to guarantee port rights to Lithuania and Poland. In January 1923, the Klaipėda Revolt took place and Klaipėda region was annexed to Lithuania in 1923 under violation of the Treaty of Versailles. The subsequent incorporation of the territory brought economic prosperity to Lithuania, with the region accounting for 30% of the country's economy. However, the region's economic significance declined after economic sanctions were imposed by Nazi Germany in 1933.