Let me give but one example. Sir John Moore could never have made his terrible march from Sahagun to Coruña, but for his good fortune in the matter of rivers and bridges. When Napoleon himself got within striking reach, near Benavente, on the torrent Esla, Moore’s rearguard blew up three spans of the old bridge of Castro Gonzalo; and when the cavalry of the Imperial Guard found a deep crossing and forded the river into a wide poplared plain, Paget and the 10th Hussars galloped through their broken ranks, destroying half of them, and capturing their general Lefebvre Desnouettes. Much later, when the narrow and snowbound Pass of Piedrafita was littered with dead British troops, all killed by hunger and cold and exhaustion, Moore was befriended by the great Roman bridge of Constantino, and by the noble viaduct of Corcul between Nogales and Becerrea. Paget was left behind with the rearguard, and in brilliant actions at the bridges he checked the pursuit, while Moore marched on toward Lugo. If a French spy had blown up the bridge of Constantino and the viaduct, after hearing of Moore’s approach, the British would have been brought to a standstill, and from a desperate position there would have been little chance of escape. So the viaduct and the Roman bridge stood between victory and defeat; they saved the British and baffled the French. In fact, Moore reached Lugo without much further harrying. Not only is there a bridge of Constantino in all campaigns, but we may be sure that as no country will ever wish to be invaded the airmen scouts of the future will try to destroy all bridges beyond their own frontiers, so as to cripple the enemy’s prearranged movements. Defeat in the near future may be nothing more than a paralysis of communications, caused by bridge-wrecking airships and aeroplanes. Try to imagine what we should suffer, if we lost in a single night eight or ten of the bridges that help to unite London to Edinburgh and Glasgow. To lose the Forth Bridge alone would be a bad defeat; and yet, as I have said, there are people still who argue that bridges need no protection because their utility in war is invaluable to both sides.[136]