Hillary Clinton watched as the tension in the Hanoi Convention Centre slowly mounted.
First, the Vietnamese foreign minister rose to criticise China's actions in the South China Sea.
Then, one by one, other ministers from Asean raised similar concerns about Chinese bullying.
Sensing her moment, the US secretary of state asked to speak to the regional summit.
For the first time, she announced that Washington had a "national interest" in freedom
of navigation and international law in the South China Sea. The Chinese were irate.
Mr Yang Jiechi, the foreign minister, looked at Mrs Clinton and warned "outside powers"
to stay out of the South China Sea disputes. Turning to the other countries, he fumed:
"China is a big country. And you are all small countries. And that is a fact."
Of the 1,539,700km Mrs Clinton travelled and the 112 countries she visited as secretary
of state, the 2010 Hanoi meeting was in many ways the defining moment of her tenure.
And it provides a valuable glimpse of the worldview that the Democratic nominee would
bring to the White House if she wins the November election.
For the Obama administration, the "pivot" to Asia is its signature foreign policy initiative.
After 200 years of primarily looking east towards Europe, the US decided that its main
priority is the Asia-Pacific.
By inserting the US directly into the arguments over the South China Sea, Mrs Clinton's
Hanoi statement was, in effect, the launch of the pivot, the moment the US declared to
the region - and to Beijing - that the US would not sit aside as China tried to establish
itself as the regional leader.
The phrase itself comes from an October 2011 article in Foreign Policy magazine by
Mrs Clinton. In "America's Pacific Century", she talked about the country being at
a "pivot point". While President Barack Obama will use an Asean summit in Laos that
started yesterday to cement the pivot as part of his own legacy, the reality is that
it was very much a joint project between the President and the woman he hopes will
succeed him.