The Middle Ages saw the steady reemergence of centralized authority and technological progress. The rising feudal system reestablished a semblance of governmental authority in Europe, albeit at a localized level. A local lord ruled over his own property, often from a central castle outside of which was a village protected by walls. Serfs — at first little more than slaves — farmed the surrounding land. Mounted knights commonly made up the lord's armed retinue, riding out to defend the town when necessary.

For a time, castles were the ultimate defensive structures on Earth. But siege weaponry slowly advanced in response to them. The ultimate siege engine prior to gunpowder was the trebuchet. Trebuchets used a counterweight to generate a force that could hurl a 300-pound projectile over 300 hundred yards. Some of these machines were enormous, with counterweights in excess of 10 tons. Once properly aimed they could make short work of any wall.

The longbow — the preeminent weapon of this time — was used extensively in siege warfare on both sides of the castle wall, especially in Britain. Longbowmen were selected at and trained from childhood, and the investment was worthwhile. Men skilled in its use could fell even heavily armored knights from a distance of up to 300 yards.

Castles were not the only large buildings being constructed at this time. Advances in architecture, such as the invention of the flying buttress, made it possible to build huge cathedrals with vaulted ceilings and magnificent stained-glass windows. Many were so well constructed that they still stand today. The development of the fireplace and chimney, however, had a greater impact on society as a whole. Large, semi-public rooms with open ceilings gave way to individually heated rooms on multiple floors, which allowed people more privacy.