1230 CE

Battle of Klokotnitsa: Byzantine forces under Theodore Komnenos Doukas invade Bulgaria, breaking the peace treaty with Tsar Ivan Asen II. Theodore gathers a large army, including western mercenaries. The two armies meet near the village of Klokotnitsa. Ivan applies clever tactics and manages to surround the Byzantines. They are completely defeated; only a small force under Theodore's brother Manuel Doukas manages to escape the battlefield. Theodore is taken prisoner and is blinded. In the aftermath, Ivan quickly extends its control over most of Theodore's domains in Thrace, Macedonia and Albania. The Latin Duchy of Philippopolis and the independent principality of Alexius Slav are also captured and annexed into Bulgaria. English invasion of France: King Henry III embarks from Portsmouth with a large expeditionary force. On May 2, he arrives on the island of Guernsey, and the next day the English army lands at Saint-Malo, where Peter I (de Dreux), duke of Brittany, meets Henry to pay him homage. The English forces march through the County of Anjou, taking the castle of Mirebeau in late July. Treaty of Ceprano: Emperor Frederick II returns from the Sixth Crusade and signs a peace agreement with Pope Gregory IX at Ceprano. He agrees not to violate any territories held by the Papal States in return for Frederick's concessions in Sicily.

In the 1230s, the 13th century.