Cao Cao saw that his troops were getting out of hand under this attack, so he called a council.
Liu Ye spoke up, saying, “Let us make catapults and so destroy them.”
Cao Cao at once had models brought and set cunning workers to make these stone-throwing machines. They soon constructed some hundreds and placed them along the walls of the camp inside, just opposite the high ladders on the enemy's mounds.
then Cao Cao's troops watched for Yuan Shao's archers to ascend the towers. As soon as the archers began to shoot, all the catapults began to heave stone balls into the skies and they wrought GREat havoc. There was no shelter from the falling stones, and enormous numbers of the archers were killed. Yuan Shao's troops called these machines “Rumblers,
Discount Oakley Sunglasses,” and after their appearance the archers dared not ascend the mounds to shoot.
then Shen Pei, the strategist, thought out another plan. He set troops to tunnel under the walls into the midst of Cao Cao's camp and called this corps “The Sappers”。 Cao Cao's soldiers saw the enemy digging out pits behind the mounds and told the chief, who at once sought a counter plan from Liu Ye.
“As Yuan Shao can no longer attack openly, he is attacking secretly and is tunneling a road under ground into the midst of our camp,” said Liu Ye.
“But how to meet it？”
“We can surround the camp with a deep moat which renders their tunnel useless.”
So a deep moat was dug as quickly as possible, and when the enemy sappers arrived thereat, lo！ their labor had been in vain and the sap was useless.
Cao Cao held Guandu throughout the eighth and ninth months when, his army being worn out and provisions failing, he began to think of giving up and returning to the capital. As he could not make up his mind, he referred his difficulties by letter to Xun Yu, whom he had left to guard Xuchang. The reply he got was to this effect：
“I have received your command to decide whether to continue the campaign or retire. It appears to me that Yuan Shao assembled such large forces at Guandu with the expectation of winning a decision. You,
Oakley M Frame Sunglasses, Sir, are very weak while he is very strong. If you cannot get the better of him, he will be able to work his will on you, and this will be a crisis of the empire. Your opponents are indeed numerous, but their leader knows not how to use them. With your military genius and discernment, where are you not sure to succeed？ Now though your numbers are small, your situation is still brighter than Liu Bang's when he faced against Xiang Yu in Jungyang and Chenggao. You are securely entrenched with your hands on Yuan Shao's throat； and even if you cannot advance, that state of things cannot endure forever but must change. This is the time to play some unexpected move, and you must not miss it. The device I leave to your illustrious ingenuity.”
This letter GREatly pleased Cao Cao, and he urged upon his troops to use every effort to maintain the position.
Yuan Shao then retired some ten miles, and Cao Cao sent out scouts to ascertain his new dispositions. One of Xu Huang's officers,
Oakley Active Sunglasses, Shi Huan, captured an enemy spy and sent him to his chief. Xu Huang interrogated him and found out that a convoy of supplies was expected and that this spy and others had been sent to find out what the risks of the route were. Xu Huang went at once to tell Cao Cao.
