In 1875 an insurrection broke out in Bosnia and Herzegovina, two Christian provinces under Turkish rule. The rebellious sentiment spread to Bulgaria, and in 1876 Turkey began a policy of repression so cruel as to make all Europe quiver with horror. Thousands of its most savage soldiery were let loose upon the Christian populations south of the Balkans, with full license to murder and burn, and a frightful carnival of torture and massacre began. More than a hundred towns were destroyed, and their inhabitants treated with revolting inhumanity. In the month of June, 1876, about forty thousand Bulgarians, of all ages and sexes, were put to death, many of the children being sold as slaves in the Turkish cities. Of all the powers of Europe, Russia was the only one that took arms to avenge these slaughtered populations. England stood impassive, the other nations held aloof, but Alexander II. called out his troops, and once more the Russian battalions were set _en route_ for the Danube, with Constantinople as their ultimate goal. In June, 1877, the Danube was crossed and the Russian host entered Bulgaria, the Turks retiring as they advanced. But the march of invasion was soon arrested. The Balkan Mountains, nature's line of defence for Turkey, lay before the Russian troops, and on the high-road to its passes stood the town of Plevna, a fortress which must be taken before the mountains could safely be crossed. The works were very strong, and behind them lay Osman Pacha, one of the boldest and bravest of the Turkish soldiers, with a gallant little army under his command. The defence of this city was the central event of the war. From July to September the Russians sought its capture, making three desperate assaults, all of which were repulsed. In October the city was invested with an army of forty thousand men, under the intrepid General Skobeleff, with a determination to win. But Osman held out with all his old stubbornness, and continued his unflinching defence until starvation forced him to yield. He had lost his city, but had held back the Russian army for nearly half a year and won the admiration of the world. The fall of Plevna set free the large Russian army that had been tied up by its siege. What should be done with these troops, more than one hundred thousand strong? The Balkans, whose gateways Plevna had closed, now lay open before them, but winter was at hand, winter with its frosts and snows. An attempt to cross the mountains at this time, even if successful, would bring them before strong Turkish fortresses in midwinter, with a chain of mountains in the rear, over which it would be impossible to maintain a line of supplies. The prudent course would have been to put the men into winter quarters at the foot of the Balkans on the north and wait for spring before venturing upon the mountain passes.