You may remember Obama's state of the Union speech in 2010, http://www.politico.com/news/stories/0110/32111_Page2.html ), and his and Pentagons «Pivot to East Asia» in 2012. This changed China's foreign policy.
Yan Xuetong explains the change in the article «From Keeping a Low Profile to Striving for Achievement»: http://cjip.oxfordjournals.org/content/7/2/153.full#fn-41
