His reign was marked by the Thirty Years' War during which he obtained the title of a prince-elector of the Holy Roman Empire at the 1623 Diet of Regensburg.

Maximilian was a capable monarch who, by overcoming the feudal rights of the local estates (Landstände), laid the foundations for absolutist rule in Bavaria.

[1] As the ablest prince of his age he sought to prevent Germany from becoming the battleground of Europe, and although a rigid adherent of the Catholic faith, was not always subservient to the church.

[1] Maximilian refrained from any interference in German politics until 1607, when he was entrusted with the duty of executing the imperial ban against the free city of Donauwörth, a Protestant stronghold.

Under his leadership an army was set on foot, but his policy was strictly defensive and he refused to allow the League to become a tool in the hands of the House of Habsburg.

Anxious to curtail the area of the struggle, he made a treaty of neutrality with the Protestant Union, and occupied Upper Austria as security for the expenses of the campaign.

[1] Attempting to remain neutral during the war, Maximilian signed the secret Treaty of Fontainebleau (1631) with the Kingdom of France, but this proved worthless.

[citation needed] Early in 1632 Gustavus Adolphus of Sweden marched into the electorate and occupied Munich, and Maximilian could only obtain the assistance of the Imperial troops by placing himself under the orders of Wallenstein, now restored to the command of the emperor's forces.

[citation needed] In March 1647 Maximilian concluded the Truce of Ulm (1647) with France and Sweden, but the entreaties of Ferdinand III, Holy Roman Emperor led him to disregard his undertaking.

Maximilian acquired numerous paintings of Albrecht Dürer, Peter Paul Rubens and additional artists for the Wittelsbach collection.

Among his court artists were Peter Candid, Friedrich Sustris, Hubert Gerhard, Hans Krumpper, Adrian de Vries and Georg Petel.