According to Fichtner, Maximilian failed to achieve his three major aims: rationalizing the government structure, unifying Christianity, and evicting the Turks from Hungary.

Maximilian's relations with his uncle worsened, as Charles V, again embattled by rebellious Protestant princes led by Elector Maurice of Saxony, wished his son Philip II of Spain to succeed him as emperor.

This arrangement was not carried out, and is only important because the insistence of the emperor seriously disturbed the harmonious relations that had hitherto existed between the two branches of the Habsburg family; an illness that befell Maximilian in 1552 was attributed to poison given to him in the interests of his cousin and brother-in-law, Philip II of Spain.

In 1551 Maximilian attended the Council of Trent and the next year took up his residence at the Hofburg palace in Vienna, celebrated by a triumphal return into the city with a large entourage including the elephant Suleiman.

While his father Ferdinand concluded the 1552 Treaty of Passau with the Protestant estates and finally reached the Peace of Augsburg in 1555, Maximilian was engaged mainly in the government of the Austrian hereditary lands and in defending them against Ottoman incursions.

In Vienna, he had his Hofburg residence extended with the Renaissance Stallburg wing, the site of the later Spanish Riding School, and also ordered the construction of Neugebäude Palace in Simmering.

However, in Vienna he became very intimate with Sebastian Pfauser [de], a court preacher influenced by Heinrich Bullinger with strong leanings towards Lutheranism, and his religious attitude caused some uneasiness to his father.

Fears were freely expressed that he would definitely leave the Catholic Church, and when his father Ferdinand became emperor in 1558 he was prepared to assure Pope Paul IV that his son should not succeed him if he took this step.

He was unable, however, to obtain the consent of Pope Pius IV to the marriage of the clergy, and in 1568 the concession of communion in both kinds to the laity was withdrawn.

On his part Maximilian granted religious liberty to the Lutheran nobles and knights in Austria, and refused to allow the publication of the decrees of the Council of Trent.

He refused to accede to the demands of the Lutheran princes; on the other hand, although the increase of sectarianism was discussed, no decisive steps were taken to suppress it, and the only result of the meeting was a grant of assistance for the war with the Turks, which had just been renewed.

With neither side winning a decisive engagement, Maximilian's ambassadors Antun Vrančić and Christoph Teuffenbach met with the Ottoman Grand Vizier Sokollu Mehmed Pasha in Adrianople to negotiate a truce in 1568.

Evidence of this friendly feeling was given in 1570, when the emperor's daughter, Anna, became the fourth wife of Philip; but Maximilian was unable to moderate the harsh proceedings of the Spanish king against the revolting inhabitants of the Netherlands.

Maximilian's power was very limited; it was inability rather than unwillingness that prevented him from yielding to the entreaties of Pope Pius V to join in an attack on the Turks both before and after the victory of Lepanto in 1571; and he remained inert while the authority of the empire in north-eastern Europe was threatened.

Maximilian's policies of religious neutrality and peace in the empire afforded its Roman Catholics and Protestants a breathing space after the first struggles of the Reformation.

Yet on a personal basis he granted freedom of worship to the Protestant nobility and worked for reform in the Roman Catholic Church, including the right of priests to marry.

He implemented the Roman School of composition with his court orchestra, however, his plans to win Giovanni Pierluigi da Palestrina as Kapellmeister foundered on financial reasons.

; Archduke of Austria, Duke of Burgundy, Brabant, Styria, Carinthia, Carniola, Margrave of Moravia, Duke of Luxemburg, of the Upper and Lower Silesia, of Württemberg and Teck, Prince of Swabia, Prince of Transylvania, Count of Habsburg, Tyrol, Kyburg and Gorizia, Landgrave of Alsace, Marquess of the Holy Roman Empire, Burgovia, the Enns, the Upper and Lower Lusatia, Lord of the Marquisate of Slavonia, of Port Naon and Salines, etc.