The victory of 718 saved Constantinople from any further peril from the Arabs, but it was again in grave peril, two centuries later, when a sudden invasion of Russians in great force threatened to accomplish at a stroke what the Saracens had failed to do in three great expeditions. The King of Kiev, one of the race of Vikings that had fought their way into southern Russia, collected a huge number of ships, variously estimated from one to ten thousand, and suddenly appeared in the Bosphorus. Probably there were not more than 1500 of these vessels all told and they must have been small compared with the Christian dromons; nevertheless they presented an appalling danger at that moment. The Christian fleet was watching Crete, the army was in the east winning back territory from the Arabs, and Constantinople lay almost defenseless. The great walls could be depended an to hold off a barbarian army, but a fleet was needed to hold the waterways; otherwise the city was doomed. In the Horn lay a few antiquated dromons and a few others still on the stocks. To Theophanes the Patrician was given this nucleus of a squadron with which to beat back the Russians. Desperate and even hopeless as the situation appeared, he went to work with the greatest energy, patching up the old ships, and hurrying the completion of the new. Meanwhile the invaders sent raiding parties ashore that harried the unprotected country districts with every refinement of cruelty. In order to make each ship count as much as possible as an offensive unit, Theaphanes made an innovation by fitting out Greek fire tubes on the broadsides as well as in the bows. This may be noted as the first appearance of the broadside armament idea, which had to wait six hundred years more before it became finally established. When the new ships had been completed and the old ones made serviceable, Theophanes had exactly fifteen men of war. With this handful of vessels, some hardly fit to take the sea, he set out from the Horn and boldly attacked the Russian fleet that blocked the entrance to the strait. Never was there a more forlorn hope. Certainly neither the citizens on the walls nor the men on the ships had any expectation of a return.