May 18 – Western Schism: In response to the January 12 ultimatum by France, the antipope Benedict publishes a bull directing the excommunication of anyone, including King Charles VI, who attempted to withdraw obedience to the Avignon Papacy. The bull, "a major tactical mistake" by Benedict, gives the leaders of the University of Paris a pretext to declare those who had carried the bull to be guilty of high treason, and to accuse Benedict to be guilty of an attack on the royal dignity and national honor. King Charles then withdraws further support of Pope Benedict and proclaims the neutrality of France in the schism between Avignon and Rome.[1]
May 28 – A representative of Burma's Kingdom of Ava apologizes to the Ming dynasty Emperor of China for the kingdom's occupation of China's vassals, the Shan States, particularly the Mongyang State, whose monarch was killed in 1406.[5]
June 15 – After receiving the news that France will no longer support his Avignon Obedience, the Antipope Benedict XIII issues the Bull Celestis altitudo, summoning the a council to meet on November 1 at the French city of Perpignan, and then flees from the French-controlled Italian region of Genoa to avoid arrest.[6]
July–December
July 2 – From Livorno, a group of 13 Roman Catholic Cardinals allied with Pope Gregory begins sending encyclical letters "to the princes and prelates of the Christian world" summoning them to the Council of Pisa, to take place on March 25, 1409, in order to end the Western Schism.[7]
August 20 – Abdul Majid Hassan, the Sultan of Brunei, sets off on a voyage to China at the invitation of the Yongle Emperor[8] and arrives in the capital, Nanjing, by September, becoming the first foreign monarch to make a peaceful visit the Chinese Empire. While visiting, the Sultan becomes ill and dies on October 19.