"They've opened the ball," exclaimed Kirkwood, as the monitor on the left of the line let fly with her 14-inch gun. "An obvious performance," remarked Fuller. "Unless one were both blind and deaf. More to the point: why are we being held in reserve, I wonder?" "Dunno," added another flying-officer. "In the case of you three fellows there might be a plausible explanation. You've been so jolly keen on getting away from the ship that the skipper won't give you another chance. By Jove! That was a good one!" Somewhere in the vicinity of Zeebrugge a dense cloud of black smoke had been hurled hundreds of feet into the air. One of the British shells had found a particularly satisfying target, for either a petrol depôt or an ammunition "dump" had been sent sky-high, with, possibly, a few hundred Huns to boot. Yet no sound of the explosion could be heard, for the monitors' guns outvoiced that. The coast-defence craft were letting fly as quickly as the hydraulic loaders performed their task, and the gigantic yet docile weapons could be trained upon the practically invisible objective. It was by no means a one-sided action. From cunningly concealed shore batteries, that seemed to multiply with hydra-headed persistence, German shells hurtled through the air, for the most part ricochetting harmlessly. A few, however, "got home." One monitor, listing badly to starboard, was already crawling slowly out of range. Another had been set on fire, but, the conflagration being quickly subdued, she "carried on" with calm and awful deliberation. It had been one of the tenets of war that armoured ships were more than a match for shore batteries. The mobility of the former and the knowledge of the fixed position of the latter accounted for the theory--a theory that had been justified by the bombardment of Alexandria. But in the greatest war that the world has yet seen this idea received a rude shock. The skill with which huge guns can be loaded, ranged and trained upon a moving target rather more than equalised matters. Thus the old forts on the Dardanelles were quickly reduced to a heap of ruins by the guns of the "Queen Elizabeth," but this did not prevent the Turks bringing heavier ordnance to bear upon the Allied squadrons as they attempted in vain to force the historic Straits. But there has been yet another swing of the pendulum. In an engagement betwixt ships and forts there was a deciding factor--the command of the air. Provided airmen from the attacking squadron could assist by observing the hits of the naval guns and by dropping quantities of powerful explosives on the hostile batteries the advantage would rest with those who held command of the sea. Nor was mere observing and bomb-dropping on defended positions sufficient. It was necessary to harass the enemy's lines of communication and prevent reserves of men and ammunition being rushed up to the coast.