Making a last effort, the American submarine rose to the surface, sent up all the recognition signals the officers could think of, and this time with success. The destroyer approached, the commander shouting from the bridge: "Who are you?" "American submarine _A L-10_." "Good luck, old man," came a now familiar voice from the bridge. "This is Bill." The commander of the destroyer and the commander of the submarine had been room-mates at Annapolis! In other ways our submarine force passed through the same experiences as the Germans. Its adventures shed the utmost light upon this campaign against merchantmen which the Germans had depended upon to win the war. The observer at the periscope was constantly spotting huge Allied merchantmen making their way into port. The great ships sailed on, entirely oblivious of the periscope and the eye of the British or American watcher fixed upon them. "How easy to sink her!" the observer would say to himself. This game in which the Germans were engaged was a dangerous one, because of Allied anti-submarine craft; but, when it came to attacking merchant ships, it was the easiest thing in the world. After a few weeks in a submarine, it grew upon our men that the wonder was not that the Germans had sunk so many merchant ships, but that they had sunk so few. Such an experience emphasized the conviction, which was prevalent in both the British and American navies, that the Germans were not particularly skilful at the occupation which seemed to be so congenial to them. Indeed, there are few things in the world that appear so absolutely helpless as a great merchant ship when observed through the periscope of an under-water boat.