By this time the weaker coast tribes had become practically extinct, and the more powerful tribes of the interior were beginning to take the alarm, as they saw the restless borderers pushing every year farther into the Indian country. As early as 1748 Dr Thomas Walker, with a company of hunters and woodsmen from Virginia, crossed the mountains to the southwest, discovering and naming the celebrated Cumberland gap and passing on to the headwaters of Cumberland river. Two years later he made a second exploration and penetrated to Kentucky river, but on account of the Indian troubles no permanent settlement was then attempted. [76] This invasion of their territory awakened a natural resentment of the native owners, and we find proof also in the Virginia records that the irresponsible borderers seldom let pass an opportunity to kill and plunder any stray Indian found in their neighborhood. In 1755 the Cherokee were officially reported to number 2,590 warriors, as against probably twice that number previous to the great smallpox epidemic sixteen years before. Their neighbors and ancient enemies, the Catawba, had dwindled to 240 men. [77] Although war was not formally declared by England until 1756, hostilities in the seven year's struggle between France and England, commonly known in America as the "French and Indian war," began in April, 1754, when the French seized a small post which the English had begun at the present site of Pittsburg, and which was afterward finished by the French under the name of Fort Du Quesne. Strenuous efforts were made by the English to secure the Cherokee to their interest against the French and their Indian allies, and treaties were negotiated by which they promised assistance. [78] As these treaties, however, carried the usual cessions of territory, and stipulated for the building of several forts in the heart of the Cherokee country, it is to be feared that the Indians were not duly impressed by the disinterested character of the proceeding. Their preference for the French was but thinly veiled, and only immediate policy prevented them from throwing their whole force into the scale on that side. The reasons for this preference are given by Timberlake, the young Virginian officer who visited the tribe on an embassy of conciliation a few years later: