During wartime, one of the most effective weapons in any country’s arsenal is sabotage: attacking the war engine itself by crippling key supplies, manufacturing, strategic locations and even logistic routes.

Saboteurs are not always an obvious and visible enemy. Many are underground agents, unconnected to official military authorities. More often than not, though, they have been trained and unofficially sanctioned by intelligence agencies or senior members of the armed forces.

The German government turned to sabotage during World War I in an attempt to thwart U.S. trade with Europe. German agents working on U.S. soil targeted munitions factories and plants producing goods to be shipped to help the Allied troops on the battlefields of Europe.

Throughout 1916 a number of mysterious fires and explosions broke out but none as brazen as the attack on Black Tom Island, a 15-minute ferry ride from the southern tip of Manhattan.

On July 30, 1916, German agents set fire to a complex of warehouses and ships to halt the movement of supplies to Europe. The explosion rocked New York City, windows shattered in downtown Manhattan and the noise was heard as far away as Maryland. The property damage was estimated at $20 million (around $377 million today).

At the time authorities downplayed the incident and many ordinary New Yorkers were unaware they were under attack, despite the continued strikes on strategic facilities.

A few months later in January 1917 a fire at the Kingsland munitions factory in New York destroyed 1.3 million artillery shells. In March there was an explosion at the U.S. Navy Yard at Mare Island, California, involving barges filled with munitions, killing 6 and injuring 31.

While the attacks were aimed at forcing the United States to back out, they instead ended up being a significant factor in the eventual deployment of U.S. troops to Europe.

By World War II sabotage had evolved and become more sophisticated. Nations organized agencies who were trained to attack military targets and disable the enemy’s war effort.

Britain used sabotage to great effect by establishing the Special Operations Executive (SOE). One of their primary functions was the sabotage of enemy equipment, installations and means of production.

They ran secret training schools, where saboteurs were schooled in creating chaos and specially trained in unarmed combat and demolition, handling weapons and explosives.

One of the most successful SOE stings was Operation Jaywick where agents disguised as Malay fisherman snuck into Singapore Harbour and sunk 30,000 tons of Japanese shipping.

Anti-German resistance and partisan movements were also active saboteurs. By the end of 1942 around 200,000 partisans were attacking factories, military installations, railroads and bridges. Many of their actions were minor forms of sabotage, such as disabling German telephone lines.

Others were more advanced such as Groupe G, a sabotage team headed by scientists and engineers at the University of Brussels. They organized attacks on the Belgian transportation network, particularly railroads and waterways, electricity supplies and telephone communications.

Today sabotage has been replaced by what is perceived as a bigger threat to nations: terrorism. While sabotage avoided human casualties and focused on crippling the arteries of the war machine, terrorists strike at the heart – the people.

Image: Black Tom Pier after the explosion, source: CIA