to ratify the Treaty of Versailles. March 23 – Admiral Miklós Horthy declares that Hungary is a monarchy, without anyone on the throne. March 25 – Irish War of Independence: British recruits to the Royal Irish Constabulary begin to arrive in Ireland. They become known from their improvised uniforms as the "Black and Tans". March 26 – The German government asks France for permission to use its own troops against the rebellious Ruhr Red Army, in the French-occupied area. March 28 – The 1920 Palm Sunday tornado outbreak hits the Great Lakes region and Deep South of the United States. March 29 – Sir William Robertson is promoted to Field Marshal, the first man to rise from private (enlisted 1877) to the highest rank in the British Army. April April – The Spanish Flu ends with an estimate between seventeen million to fifty million dead. It would be the last global pandemic until the 2009 swine flu pandemic almost 90 Years Later. April 2 – The German army marches to the Ruhr, to fight the Ruhr Red Army. April 3 – Attempts are made to carry out the failed assassination attempt on General Mannerheim, led by Aleksander Weckman by order of Eino Rahja, during the White Guard parade in Tampere, Finland. April 4 – 1920 Palestine riots: Violence erupts between Arab and Jewish residents in Jerusalem; 9 are killed, 216 injured. April 6 – The short-lived Far Eastern Republic is declared, in eastern Siberia. April 11 – Mexican Revolution: Álvaro Obregón flees from Mexico City (during a trial intended to ruin his reputation) to Guerrero, where he joins Fortunato Maycotte. April 19–26 – San Remo conference: Representatives of Italy, France, the United Kingdom, and Japan meet to determine the League of Nations mandates for administration of territories, following the partitioning of the Ottoman Empire. April 19 – Germany and Soviet Russia agree to the exchange of prisoners of war. April 20 Mexican Revolution: Álvaro Obregón announces (in Chilpancingo) that he intends to fight against the rule of Venustiano Carranza. The 1920 Summer Olympics open in Antwerp, Belgium. The Olympic symbols of five interlocking rings and the associated flag are first displayed at the games. April 23 – The Grand National Assembly of Turkey is founded by Mustafa Kemal Atatürk, in Ankara. It denounces the government of Sultan Mehmed VI and announces a temporary constitution. April 24 – Polish–Soviet War: Polish