This provided the Hungarians with sufficient impetus to continue to resist the Ottoman occupation, which they did for another seventy years. The Austrian branch of Habsburg monarchs needed the economic power of Hungary for the Ottoman wars. During the Ottoman wars the territory of the former Kingdom of Hungary shrunk by around 70%. Despite these territorial and demographic losses, the smaller, heavily war-torn Royal Hungary had remained economically more important than Austria or the Kingdom of Bohemia even at the end of the 16th century. Of Ferdinand's territories, the depleted Kingdom of Hungary was at that time his largest source of revenue. The subsequent near constant warfare required a sustained commitment of Ottoman forces, proving a drain on resources that the largely rural and war-torn kingdom proved unable to repay. Crusader armies besieged Buda several times during the 16th century. Sultan Suleiman himself died of natural causes in Hungary during the Battle of Szigetvár in 1566. There were also two unsuccessful Ottoman sieges of Eger, which did not fall until 1596, seventy years after the Ottoman victory at Mohács. The Turks proved unable to conquer the northern and western parts of Hungary, which belonged to the Habsburg monarchs. A book on the Turkish culture was written by Georgius Bartholomaeus with information obtained from Christian troops released by the Ottomans after the battle. Mohács is seen by many Hungarians as the decisive downward turning point in the country's history, a national trauma that persists in the nation's folk memory. To indicate magnitude of bad luck at hand, Hungarians still say: "more was lost at Mohács" (). Hungarians view Mohács as marking the end of an independent and powerful European nation. Whilst Mohács was a decisive loss, it was the aftermath that truly put an end to independent Hungary. The ensuing two hundred years of near constant warfare between the two empires, Habsburg and Ottoman, turned Hungary into a perpetual battlefield. The countryside was regularly ravaged by armies moving back and forth, in turn devastating the population. Only in the 19th century would Hungary regain some degree of autonomy, with full independence coming only after the First World War; however, the Treaty of Trianon awarded much of its former land to other states (such as Romania, Czechoslovakia, and Yugoslavia), and Hungary has never regained its former political power. In the 463 years from 1526 to 1989, Hungary spent the vast majority of the time under the direct or indirect domination of a foreign power.