U-boats were like terrorist cells in their ability to sow fear. They were invisible, ubiquitous, noiseless. To pluck off ships making the Atlantic crossing, the U-boats would place themselves across the convoy lanes and lie in wait. When a U-boat spotted a vessel, it would radio central command, which would alert other subs to close in. Some U-boat commanders were so daring that they would submerge and surface in the middle of the convoys, shooting at the Allies from the inside out. The Battle of the Atlantic was a war of lives and of commerce.
