Dwight Messimer, "The Baltimore Sabotage Cell," Eight Bells Book Lecture, Naval War College Museum, May 21, 2015.

The Imperial German Navy lacked the means to cut the British supply line with the United States. One option was to build more U-boats. The other option to stop the flow of goods was to attack the sources of the manufactured goods by sabotaging munitions factories, depots, and shipping. There were over fifty successful acts of sabotage on the East Coast prior to April 1917. Baltimore was the key city to their plan.

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