Servia and across the Danube into Wallachia, and defeated Sigismond of Hungary at the great battle of Nicopolis in 1396. Under Murad II. they spread into Macedonia and Hungary. To Mohammed II. was reserved the crowning honour of the conquest of Constantinople, but he also extended his sovereignty over Trebizond, Greece and the islands of the Ægean, Bosnia, Albania and even the Tartars of the Crimea. At the death of the great conqueror in 1481, the Turkish empire in Europe had reached the dimensions which it retained in the middle of the present century. But it still continued to grow. [Sidenote: =Suleiman the Magnificent, 1520–1566.=] Under Suleiman the Magnificent, who reigned from 1520 to 1566, it attained its greatest power. He drove the Knights-Hospitallers out of Rhodes, crossed the Danube, captured Belgrade, and turned half Hungary into a Turkish province under a pasha at Buda, while he forced the princes of Transylvania and Moldavia to pay him tribute. So powerful had he become that the powers of Europe began to realise his importance, and Francis I. of France did not disdain to purchase by his friendship the aid of the Sultan against his great enemy the Emperor, and to lay the foundations of French influence in the East by the privileges which he obtained for his countrymen at Constantinople. [Sidenote: =Alliance with France.=] From that time to the present day French policy has always had for one of its chief objects the maintenance of a group of alliances in northern and eastern Europe, which may serve to threaten Germany with the danger of being caught between two fires, should she find herself at war with France. For many years Sweden Poland and Turkey formed such a group, and the endeavour to keep them in firm friendship with France was always a leading feature of French diplomacy. In the seventeenth century, when the House of Austria was the chief opponent of France, the assistance of Poland and of the Sultan was naturally of great importance. In modern days, during the decay of the Ottoman empire and the growth of the rivalry with northern Germany, the Czar has taken the place of the Sultan as the necessary ally of France. Thus in the sixteenth century, mainly through the selfish policy of the French kings, the Ottoman Sultans found themselves admitted into friendship and alliance with European sovereigns, just at the very time when they seemed to be threatening ruin and destruction to European civilisation. [Sidenote: =Beginning of Turkish decline, 1566.=]