Crush depth

Reactionary enemy regimes have brutally taken command in South Africa and Germany. U.S. and European shipping lanes are suddenly under attack. World War is at hand -- and for the ruthless Berlin-Boer Axis, the devastating weapons of choice will be tactical nukes used at sea.The Voortrekker, a deep-diving state-of-the-art German submarine, is on the prowl, carrying more onboard firepower than many of the world's nations possess -- and the crippled sub USS Challenger is the only weapon in America's arsenal that can match up with the silent killer. But the nation's last hope is in dry dock --…