In Aug. 1493 the death of the emperor left Maximilian sole ruler of Germany and head of the house of Habsburg; and on March 16, 1494 he married at Innsbruck Bianca Maria Sforza, daughter of Galeazzo Sforza, duke of Milan (d. 1476). Maxi milian made an ineffectual appeal to the Christian sovereigns to assist him in driving the Turks from Europe. In 1494 he was again in the Netherlands, where he led an expedition against the rebels of Gelderland, assisted Perkin Warbeck to make a descent upon England, and formally handed over the Government of the Low Countries to Philip. His attention was next turned to Italy, and, alarmed at the progress of Charles VIII. in the peninsula, he signed the league of Venice in March 1495, and about the same time arranged a marriage between his son Philip and Joanna, daughter of Ferdinand and Isabella, king and queen of Castile and Aragon. In need of help in Italian war the king called the diet to Worms in March 1495 and urged the necessity of checking the progress of Charles; proposals for the better government of the empire were brought forward at Worms as a necessary pre liminary to financial and military support. Some reforms were adopted, the public peace was proclaimed without any limitation of time and a general tax was levied. The three succeeding years were mainly occupied with quarrels with the diet, with two invasions of France, and a war in Gelderland against Charles, count of Egmont, who claimed that duchy, and was supported by French troops. The reforms of 1495 were rendered abortive by the refusal of Maximilian to attend the diets or to take any part in the working of the new Constitution, and in 1497 he strength ened his own authority by establishing an Aulic Council (Reich shofrath), which he declared was competent to deal with all business of the empire, and about the same time set up a court to centralize the financial administration of Germany.
In Feb. 1499 the king became involved in a war with the Swiss, who had refused to pay the imperial taxes or to furnish a contri bution for the Italian expedition. Aided by France they defeated the German troops, and the peace of Basle in Sept. 1499 recog nized them as virtually independent of the empire. About this time Maximilian's ally, Ludovico of Milan, was taken prisoner by Louis XII., king of France, and Maximilian was again com pelled to ask the diet for help. An elaborate scheme for raising an army was agreed to, and in return a council of regency (Reichs regiment) was established, which amounted, in the words of a Venetian envoy, to a deposition of the king. The relations were now very strained between the reforming princes and Maximilian, who, unable to raise an army, refused to attend the meetings of the council at Nuremberg, while both parties treated for peace with France. The hostility of the king rendered the council impotent. He was successful in winning the support of many of the younger princes, and in establishing a new court of justice, the members of which were named by himself.
The negotiations with France ended in the Treaty of Blois, signed in Sept. 1504, when Maximilian's grandson Charles was betrothed to Claude, daughter of Louis XII., and Louis, invested with the duchy of Milan, agreed to aid the king of the Romans to secure the imperial crown. A succession difficulty in Bavaria
Landshut was only decided after Maximilian had taken up arms and narrowly escaped with his life at Regensburg. In the settle ment of this question, made in 1505, he secured a considerable increase of territory, and when the king met the diet at Cologne in 1505 he was at the height of his power. His enemies at home were crushed, and their leader, Berthold, elector of Mainz, was dead; while the outlook abroad was more favourable than it had been since his accession.
But whatever hopes of a universal monarchy Maximilian may have had were shattered by the death of his son Philip and the rupture of the Treaty of Blois. The diet of Cologne discussed the question of reform in a halting fashion, but afforded the king supplies for an expedition into Hungary, to aid his ally Ladislaus, and to uphold his own influence in the East. Having established his daughter Margaret as regent for Charles in the Netherlands, Maximilian met the diet at Constance in 1507, when the imperial chamber (Reichskammergericht) was revised and took a more permanent form, and help was granted for an expedition to Italy. The king set out for Rome to secure his coronation, but Venice refused to let him pass through her territories; and at Trant, on Feb. 4, 1508, he assumed the title of Roman Emperor Elect, to which he soon received the assent of pope Julius II. He attacked the Venetians, but finding the war unpopular with the trading cities of southern Germany, made a truce with the republic for three years. The Treaty of Blois which contained a secret article providing for an attack on Venice, ripened into the league of Cambray, which was joined by the emperor in Dec. 1509. He soon took the field, but after his failure to capture Padua the league broke up; and his sole ally, the French king, joined him in calling a general council at Pisa to discuss the question of Church reform.