Louis was adopted by the Holy Roman Emperor Maximilian I in 1515. When Maximilian I died in 1519, Louis was raised by his legal guardian, his cousin George, Margrave of Brandenburg-Ansbach. Following the accession to the throne of Suleiman I, the sultan sent an ambassador to Louis II to collect the annual tribute that Hungary had been subjected to. Louis refused to pay the annual tribute and had the Ottoman ambassador executed and sent the head to the Sultan. Louis believed that the Papal States and other Christian States including Charles V, Holy Roman Emperor would help him. This event hastened the fall of Hungary. Hungary was in a state of near anarchy in 1520 under the rule of the magnates. The king's finances were a shambles; he borrowed to meet his household expenses despite the fact that they totaled about one-third of the national income. The country's defenses weakened as border guards went unpaid, fortresses fell into disrepair, and initiatives to increase taxes to reinforce defenses were stifled. In 1521 Sultan Suleiman the Magnificent was well aware of Hungary's weakness. The Ottoman Empire declared war on the Kingdom of Hungary, Suleiman postponed his plan to besiege Rhodes and made an expedition to Belgrade. Louis failed to coordinate and gather his forces. At the same time, Hungary was unable to get assistance from other European states, which Louis had hoped for. Belgrade and many strategic castles in Serbia were captured by the Ottomans. This was disastrous for Louis' kingdom; without the strategically important cities of Belgrade and Šabac, Hungary, including Buda, was open to further Turkish conquests. After the siege of Rhodes, in 1526 Suleiman made a second expedition to subdue all of Hungary. Louis made a tactical error when he tried to stop the Ottoman army in an open field battle with a medieval army, insufficient firearms, and obsolete tactics. On 29 August 1526, Louis led his forces against Suleiman in the disastrous Battle of Mohács. The Hungarian army was surrounded by Ottoman cavalry in a pincer movement, and in the center the Hungarian heavy knights and infantry were repulsed and suffered heavy casualties, especially from the well-positioned Ottoman cannons and well-armed and trained Janissary musketeers. Nearly the entire Hungarian Royal army was destroyed on the battlefield. During the retreat, the twenty-year-old king died when he fell backwards off his horse while trying to ride up a steep ravine of the Csele stream.