One is a little surprised at the progress in the higher branches of the art of war which had clearly been made by the enemy who now assaulted Paris. The description of their means of attack, if not intelligible in every detail, at least shows that the freebooters, merciless heathens as they were, were at all events thorough masters of the engineering science of their age.[90] But, through the whole winter of 885, all their attempts were unavailing. The skill and valour of the defenders were equal to those of the besiegers, and their hearts were strung by every motive which could lead men to defend themselves to the last. But early in the next year, in February 886, accident threw a great advantage into the hands of the besiegers. A great flood in the Seine swept away, or greatly damaged, the lesser bridge, the painted bridge, that which joined the island to the fortress on the left bank of the river.[91] That fortress and the suburb which it defended, the suburb which contained the Roman palace and the ministers of Saint Genoveva and Saint German, were thus cut off from the general defences of the city. The watchful care of the Bishop strove to repair the bridge by night. But the attempt was forestalled by the invaders; the tower was isolated and surrounded by the enemy. The Bishop and the other defenders of the city were left to behold, to weep, and to pray from the walls, at the fate of their brethren whom they could no longer help.[92] The tower was fiercely attacked; the gate did not give way till fire was brought to help the blows of the Northmen; the defenders of the tower all perished either by the flames or by the sword, and their bodies were hurled into the river before the eyes of their comrades.[93] The conquerors now destroyed the tower, and from their new vantage ground they pressed the siege of the island city with increased vigour.