In 1909, when the German Kaiser was expanding the war machine of Imperial Germany, British intelligence had scant knowledge regarding the types of weapons being forged inside Germany's war plants. At the behest of British intelligence, Reilly was sent to obtain the plans for the weapons. Reilly arrived in Essen, Germany, disguised as a Baltic shipyard worker by the name of Karl Hahn. Having prepared his cover identity by learning to weld at a Sheffield engineering firm, Reilly obtained a low-level position as a welder at the Krupp Gun Works plant in Essen. Soon he joined the plant fire brigade and persuaded its foreman that a set of plant schematics were needed to indicate the position of fire extinguishers and hydrants. These schematics were soon lodged in the foreman's office for members of the fire brigade to consult, and Reilly set about using them to locate the plans.