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Submarines in war

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• Submarines in war
• Men started to think of submarine craft around the late 18th century, but the necessary technology only became available around 1900. The requirement was for a vessel that could travel quietly, stay under water for long periods and deliver attack weapons in wartime, while providing its crew with a life-support system.

Submarines did play a role during World War One, but it was only during World War Two that their full potential was realised. During that war, Nazi submarine U-boats, organised in 'Wolf Packs', came close to cutting the vital Atlantic lifeline that brought essential supplies from the United States to Britain and Europe - through their attacks on the Allies' supply ships.

The Allies' response included introducing a convoy system to accompany the ships. They also succeeded in breaking the 'Enigma' code with which the Germans transmitted secret information concerning their positions, strength and tactics, and this enabled the Allies to track the otherwise elusive enemy. Other technological developments, such as sonar, depth charges and long-range bomber aircraft, eventually ended the U-boat threat.

Nuclear submarines do not need refuelling, and this enables them to stay submerged almost indefinitely. The first nuclear submarine was USS Nautilus, launched in 1955. The US subsequently developed two types of vessels, one for torpedo attack and the other, called Trident, with a system for delivering nuclear ballistic missiles. The Soviets responded with their own submarines.

Unlike land-based systems, such missiles are not easily tracked. The ill-fated USS 'Scorpion', illustrated here, disappeared in mid-Atlantic with all crew on board in 1968, possibly due to torpedo malfunction, although there has been speculation about a clash with a Soviet submarine. So far six nuclear submarines have been lost, with their crew, most recently the Russian 'Kursk' in an accident in 2000. The ecological impact from this is not known.