 Meanwhile, Wei emperor Cao Rui ordered Sima Yi to refrain from engaging the enemy and to wait for opportunities to strike.Zhuge Liang attempted to lure Sima Yi into battle but Sima Yi followed Cao Rui's orders and remained in camp.Zhuge Liang understood that Sima Yi was trying to wear them down through attrition warfare, so he continued the "tuntian" system to sustain the Shu army.