1939 Nazi–Soviet Pact. During World War II, the island was first occupied by the Soviet Red Army in June 1940 and, along with the rest of Estonian territory, formally annexed into the Stalinist USSR in August 1940. The island was then invaded and occupied by Nazi Germany in 1941 (Operation Beowulf). German troops were expelled and the island was reoccupied by the Soviet Red Army in the Moonzund Landing Operation in October and November 1944. In 1946, the Soviet military authorities declared Saaremaa a restricted zone closed to all non-local civilians, i.e., mainland Estonians and foreigners. It remained a restricted area until 1989. Estonia regained independence in August 1991. Geography The island forms the main barrier between the Gulf of Riga and the Baltic Sea. To the south of it is the main passage out of the gulf, the Irbe Strait, next to Sõrve Peninsula, the southernmost portion of the island. In medieval times islanders crossed the strait to form fishing villages on the Livonian coast, notably Pitrags. In those days it was easier and quicker to cross the strait towards nearby Kolka, Saunags or Mazirbe, than travel by horse large distances inland. The highest point on the island is 54 m above sea level. The Kaali crater is on the island. The island has much forested terrain. One of the symbols of the island is the juniper. Nature More than 10,000 years ago the first parts of Saaremaa arose from the Baltic Ice Lake. The uplift of the Earth's crust is continuing even today at a rate of per year. The West Estonian islands are low-lying plains resting on limestone; their average elevation is roughly above sea level. Limestone has become denuded in a great number of places, resulting in cliffs, limestone pits and quarries at Mustjala, Ninase, Pulli, Üügu and Kaugatuma. Because of its mild maritime climate and a variety of soils, Saaremaa has a rich flora, illustrated by the fact that 80% of the plant species found in Estonia are represented here. Altogether 1200 species of vascular plants can be found in Saaremaa. About 120 of the local plant species are rare ones that have received special protection status. The most famous endemic species is Rhinanthus osiliensis, a rare little flower growing mostly in spring fens. Rare and beautiful flowers are widespread; out of the 36 species found in Estonia, 35 of them are found on Saaremaa