William I, Duke of Bavaria

William I, Duke of Bavaria-Straubing (Frankfurt am Main, 12 May 1330 – 15 April 1389, Le Quesnoy), was the second son of the emperor Louis IV the Bavarian from his second wife Margaret of Holland and Hainaut. He was also known as William V, Count of Holland, as William III, Count of Hainaut and as William IV, Count of Zeeland.

In 1345 William's father was conferring Hainaut, Holland, Zeeland and Friesland upon his wife Margaret, and shortly later also upon their son William. After his father's death in 1347 William ruled Bavaria, Holland and Hainaut together with his five brothers until 1349. With the first division of the Wittelsbach possessions in 1349 he received Hainaut, Holland and Lower Bavaria together with his brothers Stephen II and Albert I. After the next division of Bavaria in 1353 he ruled together with his younger brother Albert I in Bavaria-Straubing, Holland and Hainaut.

William had engaged in a long struggle with his mother Margaret, obtaining Holland and Zeeland from her in 1354, and Hainaut on her death in 1356.

In 1350, the nobles of Holland asked Margaret to return to Holland again. She then battled for the power in Holland and Hainaut for some years with her son William who refused to pay her alimony. The Cod league was formed on 23 May 1350 by a number of supporters of William. On 5 September the same year, the Hook league was formed. Soon afterward, these factions clashed, and a civil war began.

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