The federal Bureau of Investigation before Hoover

With the outbreak of World War I in Europe in August 1914, the agents of the Bureau of Investigation suddenly had their hands full to investigate German intrigue. Initially, the German government sought to smuggle German reservists to the Fatherland and supply the remnants of the Imperial fleet from US shores. As American military supplies to the Allies showed effects on the battlefields of Europe, German agents weaponized the Mexican Revolution, infiltrated the labor and peace movements, and attacked US manufacturing and shipping. In a steep learning curve, the Bureau moved from law enforcement to intelligence and counterintelligence work.