The plateau surrounding Sebastopol is seamed with deep ravines running more or less northwards down to the sea, some of them three or four miles in length. By these ravines the various portions of the besieging lines were separated from each other, more completely in proportion as the works were brought nearer to the city. Thus some little time must elapse before any one portion could be largely reinforced. The Russians hoped, by bringing a very strong force to bear upon the English troops occupying the bit of the plateau between the last of these ravines and the valley of the Tchernaya, to overwhelm them before they could be adequately supported, and so establish themselves on the plateau. If they could do this, the allies must fight a general action with their backs to the sea, that is to say with the certainty of destruction if they were defeated. From this necessity the allies were saved by the obstinate valour of the English infantry, who fought in what is known as the battle of Inkerman.[87] At the beginning of November Prince Menschikoff had at his disposal more than 100,000 men, exceeding the forces of the allies in the proportion of at least three to two. He thus had good reason for hoping to turn the tables on his enemies; and had his combinations been made with more skill, he might well have succeeded. His plan was that nearly 20,000 infantry with a quantity of artillery should issue from Sebastopol and assail Mount Inkerman, in conjunction with a somewhat smaller force from outside, which should cross the Tchernaya by the great bridge at its entrance into the harbour. At the same time the remainder of the field army under Gortschakoff was to demonstrate from the Tchernaya valley against the whole east side of the allied position; and the ample garrison of Sebastopol was to be in readiness to assault the siege works if they were denuded of troops. He forgot that every movement of Gortschakoff down in the valley could be fully seen from the plateau, and that therefore demonstrations were futile. A real attack in all quarters at once might, with his very superior numbers, have been made without risk: but he was not the man to depart from conventional methods. Similarly in planning the actual attack, he was swayed by the conventional, and usually sound, objection to sending troops into action divided by an obstacle which prevents all communication. Mount Inkerman was obviously to be assailed by ascending both from the Tchernaya on the east and from the great ravine on the west, known as the Careenage ravine. The forces detailed for this purpose would have amply sufficed to attack simultaneously the tongue of land west of the Careenage ravine also: but the Russian general was afraid to divide his troops by this very steep ravine, forgetting that Sebastopol with its large garrison lay behind, and committed the far worse error of crowding all his men into the one attack, where there was not room for half of them.