The Icelandic NATO riot of March 30, 1949 is arguably the most famous riot in Icelandic history. It was prompted by the decision of Alþingi, the Icelandic parliament, to join the newly formed NATO, thereby involving Iceland directly in the Cold War, opposing the Soviet Union and re-militarizing the country. The protesters first convened behind Miðbæjarskóli, a school in the centre of Reykjavík and then marched on Austurvöllur, a small park in front of the parliament building, where a throng of people had already arrived positioning themselves between the parliament and the rioters, intending to defend it. At first the demonstrators were calm, but when a leading member of the Socialist Party announced over a loudspeaker that the leader of his party was held hostage inside the Parliament building, things became violent. Rocks were tossed at the building, some breaking the windows and one narrowly missing the head of the Parliamentary president, until the Reykjavík police force, aided by volunteers from the Independence Party intervened, beating rioters down and eventually launching tear gas grenades at the mob.