Alexander's next movements from Embolina most clearly indicate that he had to deal with a mountain position. There is no getting away from it, nor from the fact that the road to it was passable for horsemen, and therefore not insuperably difficult. At the same time he had to move as slowly as any modern force would move, for he was traversing the rough spurs of a hill which ran to 7800 feet in altitude. Further, the mountain was high enough to render signalling by fire useful. The "rock" was obviously either a mountain itself or it was perched on the summit of a mountain. Ptolemy as usual had conducted the reconnaissance. He established himself unobserved in a temporary position on the crest, within reach of the enemy, who attempted to dispossess him and failed; and it was he who (according to the story) signalled to Alexander. Ptolemy had followed a route, with guides, which proved rough and difficult, and Alexander's attempt to join him next day was prevented by the fierce activity of the mountaineers, who were plainly fighting from the mountain spurs. Then, it is said, Alexander communicated with Ptolemy by night and arranged a combined plan of attack. When it "was almost night" of the following day Alexander succeeded in joining Ptolemy, but only after severe fighting during the ascent. Then the combined forces attacked the "rock" and failed. All this so far is plain unvarnished mountain warfare, and the incidents follow each other as naturally as in any modern campaign. It becomes clear that the "rock" was a position on the crest of a high mountain, the ascent of which was rendered doubly difficult by fierce opposition. But it was practicable. Nothing is said about cavalry ascending. Why, then, did Alexander take cavalry? This question leads to another. Why do our frontier generals always burden themselves with cavalry on these frontier expeditions? They cannot act on the mountain-sides, and they are useless for purposes of pursuit. The answer is that they are most valuable for preserving the line of communication. Without the cavalry Alexander had no overwhelming force at his disposal, and it would not be very hazardous if we assumed that the force which actually reached the crest of the mountain was a comparatively small one--much of the original brigade being dispersed on the route.