5. Operation Pastorius
Operation Pastorius was, in fact, a response to the successful explosion that rocked Black Tom island. In 1942, German intelligence agents had begun to make their way into the US. Using saboteurs on the inside, the Germans wanted them to take down various targets in the US, like hydroelectric plants at Niagara Falls and multiple railroad stations along the East Coast.
Despite months of planning, the mission never reached its full potential. After all, the American authorities were hip to the saboteurs. Once the Coast Guard caught and questioned one of the Germans, who was in fact hoping to defect to the US all along, the authorities arrested the other saboteurs. Fortunately for the US, the Nazi mission was never truly carried out.
4. The Orleans, Massachusetts Attack
Throughout WWI, German U-boats were constantly sinking American ships out in open water. However, by the summer of 1918, the US had to fully take action against the Germans, who were directly targeting the East Coastline.
On July 21, the German U-Boat 156 appeared in the middle of Cape Cod, close to the seaside town of Orleans, Massachusetts, and swiftly started firing at the shoreline. As shells descended on the beach, the US military quickly responded, prepared to fight back.
Naval airplanes also came to the aid of US troops on the ground, dropping loads of explosives on the German submarine. Quickly understanding their losing position, the U-boat retreated, heading north to escape the enemy aircraft, and the Americans eventually lost its location.