Events Thomas II of Savoy becomes count of Flanders. Elbląg, Poland's founded. Representatives of all 4 khanates lead 150,000 Mongol, Turkish and Persian troops into Europe. 21 December – Mongol invasion of Rus' – Sack of Ryazan. Gualdo Tadino, Italy,'s destroyed by fire. The County of Artois's founded in France. Baldwin II becomes Latin Emperor of Constantinople. Conrad IV of Germany becomes King of Germany. The Livonian Brothers of the Sword unite with the Teutonic… (More on 1237)