By the Treaty of Adrianople the Black Sea was opened to the commercial vessels of all nations. This made for the rapid economic development of the principalities by providing an outlet for their agricultural produce, the chief source of their wealth. It also brought them nearer to western Europe, which began to be interested in a nation whose spirit centuries of sufferings had failed to break. Political, literary, and economic events thus prepared the ground for the Rumanian Renascence, and when in 1848 the great revolution broke out, it spread at once over the Rumanian countries, where the dawn of freedom had been struggling to break since 1821. The Rumanians of Transylvania rose against the tyranny of the Magyars; those of Moldavia and Muntenia against the oppressive influence of Russia. The movement under the gallant, but inexperienced, leadership of a few patriots, who, significantly enough, had almost all been educated in France, was, however, soon checked in the principalities by the joint action of Russian and Turkish forces which remained in occupation of the country. Many privileges were lost (Convention of Balta Liman, May 1, 1849); but the revolution had quickened the national sentiment of the younger generation in all classes of society, and the expatriated leaders, dispersed throughout the great capitals of Europe, strenuously set to work to publish abroad the righteous cause of their country. In this they received the enthusiastic and invaluable assistance of Edgar Quinet, Michelet, Saint-Marc Girardin, and others.