Louis IV the Bavarian vs Philip I of Castile

Louis, Duke of Bavaria, was elected King of Germany by a faction of electors, while Frederick the Fair of Habsburg was elected by another faction. This led to a double election and civil war.

Louis IV decisively defeated his rival Frederick the Fair at the Battle of M

Pope John XXII excommunicated Louis IV for exercising imperial authority without papal approval. Louis responded by declaring the pope a heretic and invading Italy, leading to a prolonged conflict between empire and papacy.

Louis IV issued the Declaration of Rhense, asserting that the German king's authority derived from election by the prince-electors, not papal approval. This strengthened the independence of the German monarchy.

Philip I of Castile married Joanna of Castile, the daughter of Ferdinand II of Aragon and Isabella I of Castile. This marriage was part of a double alliance between Spain and the Habsburgs, strengthening ties between the two dynasties and eventually bringing the Spanish throne to the Habsburg family.

Upon the death of Isabella I of Castile, Philip I and Joanna became the nominal rulers of Castile. However, Ferdinand II of Aragon disputed their claim, leading to a power struggle. Philip traveled to Castile to assert his authority, but his reign was brief.

Philip I of Castile and Ferdinand II of Aragon signed the Treaty of Villaf

Philip I of Castile died suddenly at the age of 28 in Burgos, possibly from typhoid fever or poisoning. His death left Joanna as the sole ruler of Castile, but her mental instability led to her confinement and the eventual assumption of power by her father Ferdinand II.