It is necessary to revert to Solyman’s feats in other directions. In 1534 he entered upon his sixth campaign, this time against Persia. Shah Ismail was no longer alive, and had been succeeded by Shah Talmasp, a very weak personage. Solyman, as a prelude to his attack, gave orders for the execution of all the Persian prisoners at Gallipoli. Ibrahim was sent on, in advance, by some months, with a large army. Instead of marching by Aleppo to Bagdad, he took the route direct to Tabriz, which he occupied without resistance on the part of the Persians. He wintered there, and the next spring he was joined by Solyman with another army, and together they marched to Mossul and Bagdad, through a most difficult country, where the climate entailed great losses on the army. Bagdad was ultimately reached. It was treacherously surrendered by its commander. In fact, the Shah made no attempt to repel the invasion of the Ottoman army, and the two great provinces of Mossul and Bagdad were added to the Ottoman Empire, without any pitched battle on the part of Persia. There were other campaigns in Persia in 1548, 1553, and 1554, in which the Turks often suffered more from the climate and from the difficulty of obtaining supplies than from the guerrilla attacks of the Persians. But there was no pitched battle between the armies of the two Powers. The Turks maintained their conquests, and have done so to the present year (1917). Not less remarkable during the long reign of Solyman than his conquests by his army were the exploits of his navy. It achieved victory in many hard-fought battles with Spain and Venice. There was no great disparity in naval force between the Turks and the Spaniards, but when the fleets of Venice and the Pope were combined with those of Spain, there was great superiority on their part in the number and size of vessels. In spite of this, in the two great battles where this combination was against them, the Turks were victorious, and generally, throughout Solyman’s reign, his fleets maintained a supremacy in the Mediterranean. This enabled him to add to his Empire the provinces of Algiers, Oran, and Tripoli, and numerous islands in the Ægean Sea, taken from Venice.