Peter upon this sent to demand satisfaction of the emperor Hussein, who was then disputing the throne with the rebel Mahmoud, who had usurped it, and likewise of Mahmoud himself. The former of these was willing to do the czar justice, the other refused it; Peter therefore resolved to right himself, and take advantage of the distractions in the Persian empire. Mir-Mahmoud still pushed his conquests in Persia. The sophi hearing that the emperor of Russia was preparing to enter the Caspian Sea, in order to revenge the murder of his subjects at Shamache, made private application to him, by means of an Armenian, to take upon him at the same time the defence of Persia. Peter had for a considerable time formed a project to make himself master of the Caspian Sea, by means of a powerful naval force, and to turn the tide of commerce from Persia and a part of India through his own dominions. He had caused several parts of this sea to be sounded, the coasts to be surveyed, and exact charts made of the whole. He then set sail for the coast of Persia the 15th day of May, 1722. Catherine accompanied him in this voyage, as she had done in the former. They sailed down the Wolga as far as the city of Astracan. From thence he hastened to forward the canals which were to join the Caspian, the Baltic, and the Euxine seas, a work which has been since executed in part under the reign of his grandson. While he was directing these works, the necessary provisions for his expedition were arrived in the Caspian Sea. He was to take with him twenty-two thousand foot, nine thousand dragoons, fifteen thousand Cossacks, and three thousand seamen, who were to work the ships, and occasionally assist the soldiery in making descents on the coast. The horse were to march over land through deserts where there was frequently no water to be had, and afterwards to pass over the mountains of Caucasus, where three hundred men are sufficient to stop the progress of a whole army; but the distracted condition in which Persia then was, warranted the most hazardous enterprises. The czar sailed about a hundred leagues to the southward of Astracan, till he came to the little town of Andrewhoff. It may appear extraordinary to hear of the name of Andrew on the coasts of the Hyrcanian Sea; but some Georgians, who were formerly a sect of Christians, had built this town, which the Persians afterwards fortified; but it fell an easy prey to the czar's arms. From thence he continued advancing by land into the province of Daghestan, and caused manifestoes to be circulated in the Turkish and Persian languages.[115] It was necessary to keep fair with the Ottoman Porte, who reckoned among its subjects, not only the Circassians and Georgians, who border upon this country, but also several powerful vassals, who had of late put themselves under the protection of the grand seignior.