Foreign wars are difficult to avoid particularly if they interrupt the flow of commerce or pose a threat to national defense. In the nineteenth century, the goal was to avoid foreign wars if at all possible. Thomas Jefferson, recognizing the need to address national defense, particularly the defense of U.S. harbors, instigated a policy of using a fleet of gunboats as a means of protecting the coast. While Jefferson argued that the defense of the U.S. homeland was enough, others argued that the U.S. needed to be prepared to protect the seas and U.S. trade interests. While the War of 1812 proved that Jefferson’s gunboat defense was not enough to keep the U.S. out of danger, the public was still of the belief that the United States should focus on the defense of its borders rather than the preparation for future foreign wars.

The desire to protect U.S. borders while avoiding the entanglements of foreign wars was a desire difficult to achieve. Often international conflict disrupted commerce long before the U.S. coastline was threatened. Defensive policies designed to protect the homeland did not always factor in the need to export war in order to protect economic interests from being threatened. By the end of the twentieth century, the protection of strategic national interests was intrinsically entwined with the protection of economic wellbeing – domestic and international. National defense often meant transporting U.S. personnel and equipment to foreign lands rather than keeping them on U.S. shores. However, in 1916 the United States, as during Jefferson’s day, still hoped to protect its national interests by protecting its borders and remaining a neutral trading partner with Germany and with Germany’s enemies. Germany, on the other hand, did not view the U.S. policy to be in the best interest of Germany and acted accordingly.

In the years before the United States entered the war, German U-boats became a clear danger to U.S. trade and the sinking of the Lusitania made it clear that civilian travel was also risky while Europe was at war. The Zimmerman Telegram exposed Germany’s decision to view the United States as a threat, but even before the Zimmerman Telegram and the official entry of the United States into the war, Germany threatened U.S. national defense and economic security. On July 30, 1916 German saboteurs carried out a plot to destroy munitions on an island in New York Harbor. The Black Tom Explosion, as the event became known, was a clear act of war designed to disrupt U.S. military aid to Great Britain. Seven people were killed and the economic costs were valued in the millions. Yet, the United States did not immediately go to war. It would take another war and the dawn of the nuclear age to convince the public that preparing to fight on foreign lands was as vital to U.S. defense as was protecting U.S. shores.