His colleagues held him in high esteem. His methods were quiet and successful, and his participation in the offences against America's peace might have passed unproven had he not been engaged in a too-absorbing conversation one day in August, 1915, upon a Sixth Avenue elevated train. He started up to leave the train at Fiftieth Street, and carelessly left his portfolio behind him--to the tender care of a United States Secret Service man. It contained documents revealing his complicity in enterprises the magnitude of which beggars the imagination. The publication of certain of those documents awoke the slumbering populace to a feeling of chagrin and anger almost equal to his own at the loss of his dossier. And yet he stayed on in America, and returned with the ambassadorial party to Germany only after the severance of diplomatic relations in 1917, credited with expert generalship on the economic sector of the American front. Germany's military attaché to the United States was Captain Franz von Papen. His mission was the study of the United States army. In August, 1914, it may be assumed that he had absorbed most of the useful information of the United States army, which at that moment was no superhuman problem. In July of that year he was in Mexico, observing, among other matters, the effect of dynamite explosions on railways. He was quite familiar with Mexico. According to Admiral von Hintze he had organized a military unit in the lukewarm German colony in Mexico City, and he used one or more of the warring factions in the southern republic to test the efficacy of various means of warfare. The rumble of a European war sent him scurrying northward. From Mexico on July 29 he wired Captain Boy-Ed--of whom more presently--in New York to " ... arrange business for me too with Pavenstedt," which referred to the fact that Boy-Ed had just engaged office space in the offices of G. Amsinck & Company, New York, which was at that time a German house of which Adolph Pavenstedt was the president, but which has since been taken over by American interests. And he added: "Then inform Lersner. The Russian attaché ordered back to Washington by telegraph. On outbreak of war have intermediaries locate by detective where Russian and French intelligence office." The latter part of the message is open to two interpretations: that Boy-Ed was to have detectives locate the Russian and French secret service officers; or that Boy-Ed was to place German spies in those offices. Captain von Papen reported to his ministry of war anent the railway explosions: "I consider it out of the question that explosives prepared in this way would have to be reckoned with in a European war...." a significant opinion, which he changed later.