At the congress of Visegrád Charles I of Hungary mediates a reconciliation between two neighboring monarchs, John of Bohemia and Casimir III of Poland.

Charles I, also known as Charles Robert, was King of Hungary and Croatia from 1308 to his death. He was a member of the Capetian House of Anjou and the only son of Charles Martel, Prince of Salerno. His father was the eldest son of Charles II of Naples and Mary of Hungary. Mary laid claim to Hungary after her brother, Ladislaus IV of Hungary, died in 1290, but the Hungarian prelates and lords elected her cousin, Andrew III, king. Instead of abandoning her claim to Hungary, she transferred it to her son, Charles Martel, and after his death in 1295, to her grandson, Charles. On the other hand, her husband, Charles II of Naples, made their third son, Robert, heir to the Kingdom of Naples, thus disinheriting Charles.

John of Bohemia, also called the Blind or of Luxembourg, was the Count of Luxembourg from 1313 and King of Bohemia from 1310 and titular King of Poland. He is well known for having died while fighting in the Battle of Crécy at age 50, after having been blind for a decade. In his home country of Luxembourg, he is considered a national hero. Comparatively, in the Czech Republic, Jan Lucemburský is often recognized for his role as the father of Charles IV, Holy Roman Emperor, one of the more significant Kings of Bohemia and one of the leading Holy Roman Emperors.

Casimir III the Great reigned as the King of Poland from 1333 to 1370. He also later became King of Ruthenia in 1340, retaining the title throughout the Galicia–Volhynia Wars. He was the last Polish king from the Piast dynasty.

September 3 is the 246th day of the year in the Gregorian calendar; 119 days remain until the end of the year.