Over this time the way they were built changed a great deal. Most of the reasons castles changed were because attackers found new ways of breaking into them. Castle defences needed to change to keep these attackers out. The first of these castles were the Motte and Bailey Castles, however this soon became too weak. Stone Castles were introduced; these were the square keep Castle, after all the Motte could not withhold its pressure they were abandoned. They were taller than Motte's so soldiers in the castle could see the enemies far off and made it more difficult to attack. Even though they took quite a long time to build, they were stronger tougher and continue much longer. After this the people started to make outside keep Castle, which were made out of stone. It was round so it made the defenders easy to protect the castle since they could see in all directions and it was easier to organize defence. Apart from its advantages, they took a long time to build and they had a weak gateway which you could attack. Also, the heavy castle on the Motte could be collapsed which was an advantage for it. Then in 1277, people started build castles called concentric castles. They had at least two walls or even more and it was the most expensive and the strongest compared to than any other previous types of castle so it took a very long to build. Also, it was big enough to hold more men and food. In 1330, medieval people created a new type for a more comfortable life. There was less violence at that time so the most important thing was comfortableness in life.  They allowed Edward to conquer Llywelyn AP Gruffydd, the Prince of Wales. The rectangular Keep. Shortly after the Normans invaded England, they began building rectangular stone keeps.