In 1943, Hitler hatches a diabolical weapon: a bank of "superguns" housed in a massive underground complex in Nazi-occupied northern France. Together, the guns would be able to pump 600 high explosive shells 100 miles to London each hour, spelling doom for the Allies. Engineers, archaeologists, and WWII historians investigate this fearsome weapon and two audacious missions designed to destroy it.

Originally produced as an episode of Nova in 2016. Title from credits screen. Widescreen.

Preview -- Uncovering the world's biggest gun -- The Allied avengers -- The world's first drone -- A flaw in the design -- A Kennedy tragedy and silver lining.