The 'backbone' of Medieval armies was the armoured knight mounted on a horse. Norman knights wore chain mail, armour made of iron rings joined together. In the 14th century chain mail was replaced by plate armour. Metal plates were attached to each part of the body.
Norman knights carried kite shaped shields. Later in the middle Ages shields became smaller.
The Normans built wooden forts called motte and bailey castles. An artificial mound of earth was created, called a motte and the living quarters were built on top. Below was a walled yard called a bailey where food and animals were stored. The whole thing was sometimes protected by a moat.
However these early wooden forts were vulnerable to fire and later castles were built of stone. In the centre was a stone tower called a keep where the inhabitants lived. Surrounding it was a curtain wall. However even if attackers breached the curtain wall the defenders could retreat into the keep and continue to hold out.
The weakest part of a castle was its gate but there were ways of strengthening it. A building called a gatehouse was built. Often it was approached by a drawbridge over a moat. Gatehouses usually had an iron grid called a portcullis that could be raised or lowered vertically. Behind the portcullis was a covered passageway running through the gatehouse. Sometimes there was a second portcullis at the other end of the passageway.
If you got past the drawbridge and the first portcullis you would have to fight your way to the second portcullis and the defenders would not make it easy for you.
In the roof were holes through which the defenders could drop stones or pour boiling liquids.
Around the curtain wall were arrow slits called embrasures. Furthermore the tops of castle walls often had overhangs. In them were openings through which boiling liquids could be poured or stones could be dropped. They were called machicolations.
However attackers could use a variety of siege weapons. The simplest was a battering ram. The users were protected by a wooden shed but the defenders might set it on fire. They could also use a crane with giant 'tongs' to try and grab the ram.
To climb the walls you could use ladders but that was dangerous as the defenders could push them over. Attackers might use a wooden siege tower on wheels. Inside it were ladders for soldiers to climb. At the top was a drawbridge. When it was lowered the attackers could swarm over the castle walls.
Attackers could also use a kind of crane called a tenelon to get over the wall. On the end of a long wooden arm was a basket containing soldiers. The basket could be swung over the castle walls.
The attackers could also hurl missiles. A medieval catapult was powered by twisted rope. The rope was twisted tighter and tighter then released, firing a stone.
Another Medieval siege weapon was called a trebuchet. It worked by counterweight. It was a kind of see saw with a huge weight at one end and a sling containing a missile at the other. The sling was tied down and when it was released the great weight at the other end of the 'see saw' caused it to swing upwards and hurl its missile.
Attackers could also tunnel under the castle walls. The tunnels were supported by wooden props. When ready they were covered in animal fat and burned. The tunnels would collapse and hopefully so would the walls.
However in the 14th century warfare was changed by the longbow. Logbows were not new (archeologists have found examples thousands of years old). However in the 14th century the English learned to use the longbow in a new way. In the early Middle Ages archers were used to 'soften up' the enemy before knights charged. (They were used that way at Hastings). However in the 14th century the English devised a new tactic of having dismounted knights protect the archers and allowing the enemy to charge. The enemy cavalry was decimated by volleys of arrows.
The longbow was used to win great victories at Crecy (1346), Poitiers (1356), and Agincourt (1415). An archer could shoot an arrow every 5 or 6 seconds. He could shoot an arrow up to 225 metres. An arrow could penetrate armour at 90 metres. The one disadvantage of the longbow was that it took years to learn to use one properly.