This episode tells the story behind the construction and destruction of one of the most heralded World War II engineering feats: the 260-mile River Kwai railway, including the infamous bridge, in Thailand. Forced by the Japanese army to work under savage conditions, more than 100,000 Allied POWs and Asian laborers lost their lives in the building of the railway, which immediately became a top target of the Allied forces. To destroy it, they had to rely on new and relatively untested technological weapons - AZON bombs, the guided, radio-controlled precursors to the modern military's smart bombs. Using firsthand survivor testimony, modern science, a blend of reconstructions and archival footage, and never-before-seen photographs of the railway during construction, the program pieces together the real story behind the birth and death of this lost railway.