Nicholas had scarcely been crowned (1826) when war broke out between Russia and Persia; and this was followed by war with Turkey, consequent upon the Greek revolution. Silistria, a great fortress in Bulgaria, fell into the hands of the Russians, who pushed their way across the Balkan mountains and occupied Adrianople. In the meantime General Paskievitch followed up his brilliant successes in the Asiatic provinces of the Sultan's dominions by the capture of Erzeroum, and advanced to Trebizond. The peace of Adrianople, in September, 1829, checked his farther advances. This famous treaty secured to the Russians extensive territories on the Black Sea, together with its navigation by Russian vessels, and the free passage of Russian ships through the Dardanelles and Bosphorus to the Mediterranean. In addition, a large war indemnity was granted by Turkey, and the occupancy of Moldavia, Wallachia, and Silistria until the indemnity should be paid. Moreover, it was agreed that the hospodars of the principalities should be elected for life, to rule without molestation from the Porte upon paying a trilling tribute. A still greater advantage was gained by Russia in the surrender by Turkey of everything on the left bank of the Danube,--cities, fortresses, and lands, all with the view to their future annexation to Russia. The territory ceded to Russia by the peace of Adrianople included the Caucasus,--a mountainous region inhabited by several independent races, among which were the Circassians, who acknowledged allegiance neither to Turkey nor Russia. Nicholas at first attempted to gain over the chieftains of these different nations or tribes by bribes, pensions, decorations, and military appointments. He finally was obliged to resort to arms, but without complete success. Such, in brief, were the acquisitions of Russia during the reign of Nicholas down to the time of the Crimean war, which made him perhaps the most powerful sovereign in the world. As Czar of all the Russias there were no restraints on his will in his own dominions, and it was only as he was held in check by the different governments of Europe, jealous of his encroachments, that he was reminded that he was not omnipotent.