Some people will ask why, then, was it that the British Navy was not able to prevent the movement of a large army from Germany into Norway across the Skagerrak? But the conditions in the Channel and in the North Sea are in no way like those which prevail in the Skagerrak. In the Skagerrak, because of the distance, we could give no air support to our surface ships, and consequently, lying as we did close to the enemy's main air power, we were compelled to use only our submarines. We could not enforce the decisive blockade or interruption which is possible from surface vessels. Our submarines took a heavy toll but could not, by themselves, prevent the invasion of Norway. In the Channel and in the North Sea, on the other hand, our superior naval surface forces, aided by our submarines, will operate with close and effective air assistance.