There have been a lot of military exchanges between the U.S. and China going back to the 1990s. China has always been seen as getting much more out of these exchanges than the U.S.. For instance, during one such exchange during the Clinton administration, China was able to learn about key vulnerabilities of our aircraft carriers. China then purchased weapons from Russia designed to exploit the weakness. In 2000, a law was passed to supposedly prevent such lapses. However, Chinese military officers have protested the restrictions posed by the 2000 law. Nevertheless, the Obama administration has allowed Chinese officials to visit sensitive military installations.
Chinese military writings explicitly name the U.S. as their number