1230

1221 1222 1223 1224 1225 1226 1227 1228 1229 1230

political events

The Treaty of San Germano in July ends hostilities between Pope Gregory IX and Friedrich II, who is absolved from excommunication after promising to respect the papal territory and to allow freedom of election to the Sicilian clergy.

León's Alfonso IX dies childless September 24 after a 42-year reign. León accepts Ferdinand III of Castile as sovereign and he unites the two kingdoms (see 1157).

The Nicaean emperor John III Vatatzes gains support from the Bulgarian czar Ivan Asen II and defeats the despot Theodore Ducas in battle at Klokotnitsa in Bulgaria (see 1225; 1235).

Bohemia's Ottakar I dies December 15 at age 75 (approximate) after a 33-year reign in which he has won autonomy from the German king and hereditary rights for the house of Premysl. He is succeeded by his son, who will rule until 1253 as Wenceslas I.

exploration, colonization

Berlin is founded on the site of former Slavic settlements (see Hohenzollerns, 1411).

medicine

Leprosy arrives in England with returning crusaders who have accompanied Friedrich II to the Holy Land.

religion

The Teutonic Knights under the leadership of their grand master Hermann von Salza begin a long campaign to Christianize Prussians in the Baltic area (see politics, 1229; 1239).

1221 1222 1223 1224 1225 1226 1227 1228 1229 1230

Mathematics

Hispanus Petrus (a.k.a. Pope Johannes XXI) [b. c. 1205, d. c. 1277] writes Tractatus logicae, subsequently known as Summulae logicales. It becomes the most widely used book on logic until the end of the 18th century, going through almost 200 editions. See also 1122 Communication; 1620 Communication.

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