The kings, knights and warlords who travelled to the crusades and who embarked on siege warfare in the Holy Land were influenced by the design and architecture of the fortresses in the far East. King Edward I of England used this information and knowledge to design and build the massive concentric castles in England. His policy enabled the conquest of Wales. Siege warfare, the development of new weapons demanded that a castle was built considering the possibilities of both attack and defence. The designs of the massive stone castles therefore altered during the centuries when building was at its pinnacle.