He had to defend his rights in a lengthy throne quarrel, finally defeated Frederick's forces in the 1322 Battle of Mühldorf, and in 1328 received the Imperial crown; though not by the pope but by the "Roman people" led by Sciarra Colonna.

Upon his victory at Mühldorf, Louis IV took the occasion to seize the princeless Margraviate of Brandenburg, where the last Ascanian ruler Henry the Child had died without heirs in 1320.

Ignoring the claims raised by Henry's Ascanian relative Duke Rudolf I of Saxe-Wittenberg, a supporter of his Habsburg rival anyway, he appointed his eldest son, the future Louis V, margrave in 1323.

[1] To further strengthen the rule of the Wittelsbach dynasty in Northern Germany, Margrave Louis was married to Margaret (1305–1340), the eldest daughter of King Christopher II of Denmark, in 1324.

[3] Having received the Brandenburg princely territory as a fiefdom, Louis contributed to the 1338 Declaration at Rhense, emphasizing his father's rights against the interference by Pope Benedict XII.

On 10 February 1342, he married the Tyrolean countess Margaret (Margarethe Maultasch), in order to acquire her estates for the Wittelsbach family;[4] nevertheless, she was not yet divorced from her previous husband, the Luxembourg prince John Henry.

While Emperor Louis IV had the scholars William of Ockham and Marsilius of Padua defend this first "civil marriage" of the Middle Ages, Pope Clement VI, however, immediately excommunicated the couple and the scandal was known across Europe.

Though Tyrol was punished with a papal interdict, and the Bishops of Brixen and Trent strongly objected to Louis' rule, the Wittelsbachs were able to gain the support of the local nobles by granting them numerous privileges.

When Louis' son Meinhard III married Margaret of Austria, the daughter of Duke Albert II, in September 1359, he and his consort were absolved from their excommunication with the support of the Habsburg family.

He was succeeded by his son Meinhard III who died two years later, whereafter his mother Margaret bequeathed her Tyrolean estates to the Habsburg duke Rudolf IV of Austria.