the prosperity of Alsace was brought to an end in the 14th century by a series of harsh winters, bad harvests, and the Black Death. These hardships were blamed on Jews, leading to the pogroms of 1336 and 1339. In 1349, Jews of Alsace were accused of poisoning the wells with plague, leading to the massacre of thousands of Jews during the Strasbourg pogrom. Jews were subsequently forbidden to settle in the town. An additional natural disaster was the Rhine rift earthquake of 1356, one of Europe's worst which made ruins of Basel. Prosperity returned to Alsace under Habsburg administration during the Renaissance. Holy Roman Empire central power had begun to decline following years of imperial adventures in Italian lands, often ceding hegemony in Western Europe to France, which had long since centralized power. France began an aggressive policy of expanding eastward, first to the rivers Rhône and Meuse, and when those borders were reached, aiming for the Rhine. In 1299 the French proposed a marriage alliance between Blanche (sister of Philip IV of France) and Rudolf (son of Albert I of Germany), with Alsace to be the dowry; however, the deal never came off. In 1307, the town of Belfort was first chartered by the Counts of Montbéliard. During the next century, France was to be militarily shattered by the Hundred Years' War, which prevented for a time any further tendencies in this direction. After the conclusion of the war, France was again free to pursue its desire to reach the Rhine and in 1444 a French army appeared in Lorraine and Alsace. It took up winter quarters, demanded the submission of Metz and Strasbourg and launched an attack on Basel. In 1469, following the , Upper Alsace was sold by Archduke Sigismund of Austria to Charles the Bold, Duke of Burgundy. Although Charles was the nominal landlord, taxes were paid to Frederick III, Holy Roman Emperor. The latter was able to use this tax and a dynastic marriage to his advantage to gain back full control of Upper Alsace (apart from the free towns, but including Belfort) in 1477 when it became part of the demesne of the Habsburg family, who were also rulers of the empire. The town of Mulhouse joined the Swiss Confederation in 1515, where it was to remain until 1798. By the time of the Protestant Reformation in the 16th century, Strasbourg was a