Erzerum was reckoned the strongest fortress in the Turkish Empire, but amid the distractions of the Dardanelles and Mesopotamian campaigns it had escaped proper attention from the Turks and their German experts, and the Grand Duke profited by the fact that Turkish troops, relieved from the pressure at Gallipoli, were sent to Kut and not to the Caucasus. Moreover, the ordinary line of communication with Erzerum by the sea and Trebizond had been cut by the Russian destruction of Turkish shipping, and transport by land was almost as difficult as it was between the head of the Persian Gulf and Kut. The Russian communications were better, but theirs was an adventurous enterprise across mountain passes under the arctic conditions of midwinter; and few people had any inkling of its inception when Yudenitch began to move on 11 January. By the 16th he was at Kuprikeui where the road crosses the Araxes, and in a two days' battle he broke the Turkish army, driving its remnants south towards Mush and clearing the way to Erzerum. Time was required to bring up the heavy guns, but early in February the forts on Deve Boyun were under bombardment, and another Russian army advancing from the north down the valley of the Kara Su defeated a Turkish division and captured Kara Gubek on the 12th and Tafta on the 14th. From the south the Russians were also crossing the Palantuken Dagh, and the fate of Erzerum was sealed. Its evacuation was completed early on the 16th, and a few hours later the Cossacks rode into the city. To the south the Russian left entered Mush and Bitlis, gaining the northern shores of Lake Van, while their right slowly pushed along the Black Sea coast in the direction of Trebizond. In Persia, too, the Russians occupied Kermanshah and descended the pass to Khanikin and the Mesopotamian plain; but it was an adventurous body of cavalry rather than a substantial military force which joined hands with the British on the Tigris some weeks after the fall of Kut. The Russians had to some extent redeemed their failure in Europe, but others they had not been able to save. The Caucasus