It all started when the United States decided to drop thousands of mines into the port Haiphong, in a desperate act to try to shorten the war. However less than a year later dozens were set off, not by passing ships, but by the sun.
Mines are triggered to explode using a magnetic sensor that detonate the explosive if the magnetic field surrounding the mine is altered. This means that when a ship passes by, the magnetic metal hull sets off the mine. It also means that if another thing wish has a strong magnetic field were to disturb the sensors, such as a solar flare, they would go off. and this is exactly what happened on August 4th 1972.
This relates to engineering because the engineers had to design a way to set off the mines to blow up the ships but also had to work around the problem of the solar flares setting off the mines.
