Ships from countries near Germany were examined from truck to keel for contraband, or papers or literature that might convey secret messages. Passengers and crews were carefully scrutinized. Close inspection and censorship of mails and cables prevented Germany from communicating with its agents in this country, and also prevented them from sending out military information.
Outgoing ships were carefully inspected to prevent them from taking supplies or materials to Germany. Some neutral vessels had been carrying from America quantities of spare machinery and electrical parts, especially those composed of copper, brass and zinc. There was reason to believe much of this was smuggled to Germany and used in the manufacture of parts for U-boats. Radio apparatus was purchased in quantities. Ships leaving for Holland or Sweden sometimes sailed with enough lubricating oil to take them around the world. Much of it must have "leaked" into Germany. This traffic was greatly reduced, and that in contraband practically ended.
Military guards were placed around piers, no enemy or suspected aliens were allowed to work around shipping, and all dock workers were required to carry identification cards. Vessels were under government supervision during their entire stay in port.
Not only navy yards and shipyards were kept under surveillance, but all plants engaged on naval work were constantly inspected. Thus all sources of production were protected from enemy activity. For this purpose a Plant Division was created, which also reported any undesirable working conditions or lack of fire protection. This led later to the creation of the Fire Prevention Section of the War Industries Board.
Admiral Welles kept in close touch with the Director of Military Intelligence, the State and Labor Departments, and the Department of Justice. Naval attachés abroad obtained a large amount of information regarding "trading with the enemy" as well as military activities, and this was transmitted to the War Industries Board, the State and War Departments. The Bureau of War Trade Intelligence coöperated with the Navy in holding up undesirable imports and exports.
Information regarding foreign navies and ships and war developments was compiled and disseminated, in confidential publications, to all our forces afloat. Fleet, Force and Division commanders were kept informed of the activities of all fleets, Allied and enemy, of ships sunk, and tonnage destruction; of the number and tracks of submarines in the Atlantic and Mediterranean; and of all efforts made by the Allied and associated powers.
The British had a remarkably complete system which constantly improved, so that, in the latter part of the war, it was said that they were informed of the sailing of every submarine sent out from Germany, and its probable destination. We had the advantage of this, as well as the information obtained by France and Italy. We had our own agents in most foreign countries, and maintained quite a force in France.
The most important of these activities was along the coast around Brest and St. Nazaire, the centers of troop and supply traffic. German agents, it was reported, were using Belle Ile as a signal station to advise their submarines.
Convoys reported suspicious lights, and it was believed that these were informers on shore signaling to U-boats. The submarines used various disguises. One, submerged with its periscope showing, lay hidden for hours in the midst of a fishing fleet. Yet the fishermen paid so little attention to it that the French semaphore station, only a few kilometers away, was not notified. A Greek merchantman hove in sight, the U-boat fired a torpedo and the steamship was sunk.
The French authorities welcomed our intelligence officers, and together they set about developing an efficient service all along the coast. A U. S. Naval Reserve officer who spoke French fluently was attached to the staff of the French commander-in-chief in Brittany. That coast is rugged and bold, with groups of small islands. The most important is Belle-Ile-en-Mer, twelve kilometers from shore, the first land sighted by convoys going to St. Nazaire, and the last seen on their way home. At the northern end is the famous "Passage de la Tenouse," leading to the bay of Quiberon. Once through this passage and in the bay, ships were considered safe from submarines. One group of our first troop convoys was attacked three miles west of the Point des Poulin, the entrance to this passage, and several shells fired by the transports ricocheted and exploded on the rocky bluffs of the island. West-bound convoys were assembled in Quiberon Bay. Every effort was made to conceal their departure, but the information that enemy submarines seemed to obtain at times was startling. When the merchant convoy system was inaugurated, ships were instructed to anchor off Le Palais, in the lee of Belle Ile. Two days later a submarine laid mines in the roadstead. The next night ships were anchored two miles to the north, but within twelve hours mines were laid there.