How did the Forbidden City escape destruction by the Red Guards in China?

Because Premier Zhou Enlai personally protected the forbidden city and ordered army units to be stationed outside to prevent ransacking by the red guards. He ordered this in 1966 after red guards attempted to force their way into the site by ramming the gates with a truck. During most of the cultural revolution the palace was sealed and entrance denied until it was reopened for Nixon's visit. Without his intervention, it is most likely that the site would have being significantly damaged or destroyed.