During the rule of Jayavarman 7th, the Empire started to decline. This was because the Khemr had over-engineered their empire. Their irrigation system was too complicated and it had failed. The cost of war was too high as soldiers had to be fed, clothed, transported and their families look after. The nobles had a very lavish lifestyle and had to pay for guards, servants and concubines. Materials like cloth, marble, gems, and even slaves were not traded for things that the empire needed.