Early in World War II Roosevelt and Churchill became aware that Germany was stockpiling ""heavy water"" (water with double hydrogen atoms) -- a sure sign that an atomic reactor was being built. Heavy water was used to slow down neutron particle bombardment in a uranium 235 pile. Churchill gave word that the world's only heavy-water plant, at Vemork in Nazi-occupied Norway, must be destroyed. The two commando teams assigned to the raid included several Norwegians, but the airdrop missed its chosen landing spot by ten miles in the dead of winter and an arduous survival odyssey began that eventually required scrapping the original plan and devising a new attack. After terrible setbacks, the hydro plant was crippled. But the Germans managed to get it operational again and a year later a new team attacked the problem of sabotaging the heavy water supplies by sinking a ferry carrying all the water back to Germany. The utter determination of the saboteurs in both raids makes for strong readability and adventure. Gallagher writes with great clarity and avoids the British failing -- loading every line with military abbreviations and acronyms. Animated.