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Fortresses in war

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• Fortresses in war
• Stone fortifications were developed in the earliest times, and Mycenean Greece provides some good examples of massive masonry dating back to the second millennium BC. The classical Greeks also built huge stone fortifications, such as the Acropolis and the 'Long Walls' in Athens.

Hadrian's Wall, in Northumberland, is an example of the Romans' skill in stone construction, while many stone castles from medieval times still dot the European countryside. In the Renaissance, following the development of gunpowder, fortresses became more complex in outline, and lower in profile, to lessen the impact of besieging cannon. These later designs especially bear the imprint of the 17th-century French architect, Vauban.

Constantinople, depicted here being attacked by crusaders in 1204, was the capital of the Byzantine Empire from the fourth century to 1453. It was renowned for centuries as an invincible fortress, having withstood the attacks of numerous peoples - such as the Persians, Arabs, Bulgars and Russians - both by land and by sea.

For many years it was the centre of Christendom, but its citizens became arrogant and eventually succeeded in offending their fellow-Christians, crusaders who had been coming to Constantinople from 1096 onwards.

In 1203, therefore, an army of crusaders sailed to the city in Venetian ships, and captured it for the first time. The crusaders provided fierce and well-trained warriors, while the Venetians contributed the technical skills. Using their ships as siege towers, the attackers were able to conquer the city in both 1203 and 1204. This remarkable achievement has been overshadowed by Ottoman conquest of Constantinople, using gunpowder artillery in 1453.

Many stone forts continued in use right up to the 20th century. The death knell for fixed lines of fortifications came when the Germans easily overran the French Maginot Line in 1940.