Blast Rocks
Mare Island

U.S. Navy ship at Mare Island Naval Shipyard; 1901 explosion at Mare Island; Damage at Mare Island; German saboteur Lothar Witzke; German saboteur Kurt Jahnke

In July 1917, just six months after the Kingsland blast that destroyed a munitions plant and nearly half a million artillery shells, German saboteurs struck again, setting off another massive explosion at the Mare Island Naval Shipyard, just north of San Francisco. The blast – on the heels of America’s formal entry into the war – destroyed a barge loaded with munitions, killing six people and injuring more than thirty. The damage extended across a wide area of northern San Francisco Bay. It was later discovered that the operation had been the work of Lothar Witzke, a former German naval lieutenant who had been working as a mechanic at Mare Island, and Kurt Jahnke, a German-American operative and former U.S. Marine. Both men were also central players in the destruction at Black Tom Island Munitions Depot in July 1916.