The great organization built up by Von Papen and his fellows for purposes of sabotage made it imperative, upon the entry of the United States into the war, that a system should immediately be devised for the protection of those plants and workers engaged in the manufacture of munitions. With the declaration of war the United States became, almost overnight, the greatest manufacturer of war materials in the world. In every city in the land factories producing the tools of the fighter’s trade were running night and day, and other factories, hundreds of them, began to spring up as though at the wave of a magician’s wand. The nation was a-hum with feverish industry from ocean to ocean. But of what avail was this tremendous wave of manufacturing activity, of what use the expenditure of billions in the erection and operation of plants and factories, unless those plants and factories were afforded protection against fire and the acts of enemy agents? To fill this need there was organized, in July, 1917, the Plant Protection Section of the Military Intelligence Division. The system of plant protection provided, first of all, for a physical examination of the munition factories of the country with a view to minimizing the danger of their destruction by fire. Basing their plans on the estimates of the insurance companies that 85 per cent of all fires are the result of carelessness, the inspectors sent out by the section insisted, as a measure essential to the success of their work, on a systematic and wholesale house-cleaning, the wave of cleanliness which struck those American plants engaged in the manufacture of munitions during the first year of the war being directly traceable to the orders of the Plant Protection Section. The officers of the section next turned their attention to measures for the prevention of sabotage and the fomentation of labor troubles by enemy agents, which was accomplished by the introduction of what was known as the “interior organization system.” This consisted in the establishment within the plant of a complete espionage system, composed of old and trusted employees, who worked as Secret Service agents, and were unknown to one another. In cases where it was deemed necessary, this body was re-enforced by trained and experienced operatives from the Plant Protection Section, who usually obtained positions as workmen in the plant without the knowledge of the management. By this means the perpetrators of many cases of sabotage were discovered, incipient strikes were prevented, agitators and professional trouble-makers were kept under surveillance, and, if their actions warranted, were placed under arrest, and an unceasing watch kept on the movements of enemy agents. The campaign of sabotage and destruction which German sympathizers had been conducting almost unchecked was abruptly halted, for so wide-spread and efficient was the section’s organization that the enemy agent was constantly haunted by the fear that his most