The allies might perhaps have taken the north side of Sebastopol, with the aid of their fleet to engage the Russian ships, before the entrance to the harbour was blocked; but such a step would have brought them practically no nearer to the capture of the city and arsenal beyond the harbour, and would have given them no base of operations. From the nature of the case their base must be the sea, and therefore they were compelled to adopt the plan, in all respects the most expedient open to them, of marching past Sebastopol, seizing Balaclava which became the English port, and Kamiesch for the French, and beginning a regular siege of Sebastopol. The Russian communications from the city northwards were never interrupted, hardly interfered with. Thus the last great siege of what may be called the Vauban period of military history, presents the unique spectacle of a fortress never invested and yet reduced, of the resources of the defending power being poured into it till they were exhausted before the superior strength of the enemy. Two days after the battle of the Alma, the allies moved southwards. Lord Raglan's resolution of "keeping his cavalry in a bandbox," so long as they were so few, most praiseworthy on the battle-field, was inexpedient on the march; and the Russian general habitually neglected to use his cavalry. Hence Menschikoff's army quitting Sebastopol, and the allies moving on Balaclava, narrowly missed a collision which might have had very serious results. As it was, Menschikoff had advanced far enough to get out into the open country unhindered, and the allies occupied their intended position without a blow. The siege works were promptly begun, the English, roughly speaking, taking care of the east side of the city, and the French of the south. On October 17 a bombardment took place, which it was hoped might open the way to a decisive assault. The English fire inflicted enormous damage on the works, but the magazine in the principal French battery was exploded by a shell, and the Russians succeeded in silencing the other French guns, while the ships inflicted far less injury on the seaward forts than they sustained. No assault could be made, and the Russian engineer Todleben gave the first evidence of his remarkable fertility of resource, in the speed with which he repaired the damage done by the English cannonade. The Russians naturally suffered greater loss in men, being more crowded than the besiegers, and obliged to hold troops in readiness to meet a possible assault. The well-stored arsenal of Sebastopol saved them from any fear of being crippled by expenditure of material. The bombardment was renewed more than once, with much the same results: it gradually became clear that Sebastopol would not be taken without a sustained siege.