The recent visit by US Secretary of Defense Robert Gates to Beijing has been widely interpreted as marking the restart of Sino-US military ties, which were damaged by the Barack Obama administration's decision to approve a $6.4 billion arms sale package to Taiwan in early 2010.

Both sides described the visit as successful and positive and agreed to build stable military relations by taking gradual practical steps. The success of Gates' visit has also helped to create a warm and constructive atmosphere for President Hu Jintao's visit to the US this week. After a turbulent year in Sino-US military relations, things are beginning to look more sanguine.

Although analysts in China and the US perceive the overall bilateral relationship as a process of ups and downs, in which recurring difficulties are either solved or shelved in pursuit of common interests, relations between the two militaries have lagged far behind and taken an on-and-off pattern, with the military relationship going through six on-and-off cycles in the last two decades.

The US cut off all military ties as part of overall sanctions against China in 1989, both sides then suspended military exchanges because of rising tensions over Taiwan in 1995-96. China halted military exchanges after the US bombing of the Chinese embassy in Belgrade in 1999 and the US severed military ties in the aftermath of the mid-air collision near Hainan Island in southern China in 2001. And China postponed and suspended military exchange programs in October 2009 and January 2010 in protest against proposed US arms sales to Taiwan.

This on-off pattern has reflected and also aggravated the lack of trust between the two militaries. The US is wary of the economic and political influence of China and its growing military might, and the Chinese People's Liberation Army (PLA), still enduring continuous US embargoes, sanctions, and calls for transparency, finds it hard to perceive its US counterpart as a trustworthy friend.

In addition, as China's most important core national interest, Taiwan is a constant issue for the two militaries. The 2005 Anti-Secession Law states that: "the State shall employ non-peaceful means and other necessary measures to protect China's sovereignty and territorial integrity". While the US' Taiwan Relations Act of 1979 states that, the US "will make available to Taiwan such defense articles and defense services in such quantity as may be necessary". The arms sales to Taiwan, even at the time when cross-Straits relations are improving, is the single most important factor jeopardizing Sino-US military ties.