With its exterior borders secured, Schwyz began to acquire rights and land in the neighboring valley. In 1386, Schwyz invaded and occupied the town of Einsiedeln, and by 1424 the monastery was under Schwyz' control, though it retained some independence. Between 1386 and 1436, Schwyz brought under its direct control the entire March District, which became part of the canton. In 1424, Küssnacht became part of the canton. Villages and lands along Lake Zürich, including Wollerau and Pfäffikon (in 1440), Hurden and Ufenau Island all became part of the canton in the 14th and 15th centuries. King Sigismund granted Schwyz the right to High Justice over Schwyz, Einsiedeln, Küssnacht and March in 1415 as a reward for their military support against Frederick IV of Habsburg. The gradual expansion of Schwyz meant that each village entered the canton under different agreements and not all the provinces were granted the same degree of autonomy. One unique case was the town of Gersau which, while located near Schwyz, became a protectorate of the Confederacy and a semi-independent state in 1359. Gersau remained a free city-state and republic until 1817 when it was merged into Schwyz.