U.S. History/German Agents in USA 1915
I live in the UK and have come across brief references to German agents causing havoc in the USA in November and December 1915 by burning down armaments factories and destroying foodstuffs intended for the Allies in Europe, all this when the USA was officially neutral.
However I cannot find details of arrests or trials (if any). Have you got any information on these incidents?
These are pretty interesting and little-known episodes in the history of the First World War, so I appreciate your interesting question and I'll be glad to help.
This link http://www.historynet.com/world-war-i-intrigue-german-spies-in-new-york.htm
focuses on the 1916 Black Tom Explosion in New Jersey, but it also provides an overview of other acts of German sabotage prior to America formally entering the war. In that article you'll read about German agent Werner Horn who detonated a bomb on a bridge connecting the US to Canada. He was, in fact, tried and imprisoned. More information about him specifically and his fate are located at http://www.cbc.ca/news/canada/new-brunswick/werner-horn-s-st-croix-bridge-bombin
Here is a (very long) link to a digitized book. Pages 13-17 furnish a brief but comprehensive account of German activities in America intended to thwart the US's effort to aid the Allies.
This is not turning into a hyperlink but it should work if copied and pasted into an address bar:
As you'll find out, most of these cases did not result in arresting or trying the culprits because the investigations did not lead to the perpetrators - at least not until too late. Or, the investigations were not vigorously pursued because President Woodrow Wilson did not want these episodes to threaten American neutrality. However, in the case of Werner Horn, there was indeed an arrest, trial, and conviction. The article about him gives a good account.
I hope that this is helpful, Mark!