In the reign of King David, a new style of building arrived in Scotland. The Norman Lords built castles for themselves, as they had in England, as protection from the native peoples and also to emphasise their importance as the new masters in the area. The earliest castles were temporary shelters, made of wood and often erected on a hill. They were known as Motte and Bailey Castles. The motte was the hill on which they built a single tower, or keep. Sometimes the hill was man-made by digging a huge moat and throwing all the soil into the centre. The bailey was the courtyard at the foot of the hill where huts, enclosures for animals and workshops would be made for everyday use. Around the bailey they built a palisade, with an inner palisade around the keep. If there were any sign of trouble the Normans would retreat inside the keep.

Because they were made of wood original motte and bailey castles easily rotted or were set on fire. Soon stone keeps were built but these often had to be built on flat ground rather than on man-made hills because of their weight. Gradually keeps were built at the front entrance and at each corner and at the rear to make the castle much stronger. A curtain wall linked all the keeps and these castles became known as curtain wall castles.

Castles were the best means of defence for the Normans and sometimes they built close to river crossings, bridges, roads or natural harbours so that they could hold these safe for the king and charge a toll or fee.

The three royal fortresses of Edinburgh, Stirling and Dumbarton were built on rocky, volcanic sites, which were difficult to capture. Marshy areas, such as the site of Hermitage in the Borders, were difficult for an enemy to penetrate also.

Often castles were linked in some way. Tantallon and Craigmillar in the Lothians were part of a chain of fortresses, towers and beacons that protected southern Scotland from English invasion. The Scots built dozens of towers and mottes in the 1160s and the 1170s to police the wild tribes of Galloway. Many castles in the west, such as Dunstaffnage near Oban, were built to keep control of land won back from the Norse Kings. Castles might also come under attack from a baron who hoped to extend his territory by seizing a neighbouring lord’s.

A typical curtain wall castle would be home to the Lord and his Lady, their servants and the knights who generally spent their days hunting in the forests with their master. Medieval Scotland was much more sparsely populated than today and was largely covered in forests in which wild boar, deer, rabbits and game birds lived to provide sufficient food for the people. By day the men hunted, by night they ate the spoils of their labours and caroused in the Great Hall. The men would sleep in the Hall too at the end of the day. There would always be a well inside the castle and stores of food, weapons and ammunition. Bows would be waiting to be strung and arrows in their hundreds would be neatly stacked in case of attack. Guards would be on watch to give the signal if there was any likelihood of danger.

Castles began to be built with round walls as the corners were found to be the weakest point of the construction. A battering ram could make a hole in the corner into which a small fire might then be laid. The wall would be considerably weakened. Doors were weak points also and increasingly drawbridges were built which could be pulled up so that the enemy had to think of a way to cross over the moat. Portcullises were the next form of defence; in later castles up to eight might be used to trap possible enemies who would be spied upon as they entered the castle from holes in the roof linking entrance keeps.

Windows were never built on the lower part of the castle and higher up were mere arrow loops. The cross-shaped ones were for the use of crossbows when the castle came under attack and the slits for longbows. Because the walls were always wider at the base of the castle the defenders on the walls could hit the attackers with arrows, boiling pitch or oil. Liquids were usually poured through holes near the top of the walls called machicolations so that they then sprayed downwards to hit as many of the enemy as possible.

The invention of, and improvement in the design of, castles meant that attackers had to find ways to capture the castle. Besieging it was a good idea if they were in no hurry; otherwise they had to come up with a plan to destroy the castle or force the defenders out. Catapults were used to fire in rotting carcasses of e.g. horses, to spread disease. Sometimes the body of a friend of the defenders was tossed over the walls to spread panic or despondency. Otherwise siege weapons had to be built and used, such as a battering ram, or a belfry for offering protection as well as ladders for scaling the walls.

Castles were essential for kings, earls and barons from the eleventh century till about the seventeenth when gunpowder reduced their might and the mighty began to build mansions which would have comfort more in mind than protection.