The United States' decision to lift all restrictions on arms sales to Vietnam slays the ghosts of the Cold War, even as it shows how Washington is squaring up to face new challenges to its global dominance.
President Barack Obama's three-day trip to Vietnam, which ended yesterday, also highlighted two other factors: America's immense soft power, and Mr Obama's remarkable success over the past seven years in helping the US arms industry enter new markets.
In Hanoi, Mr Obama talked of removing the "lingering vestige of the Cold War". It was US diplomat George Kennan's 1950s theory - that nations would, like dominoes, fall to communism if it was not contained - that led the US into the Vietnam War. Today, the big threat it perceives is aggressive Chinese power projection, one that could spread east into the Pacific and westward into the Indian Ocean.
In this new reality, Vietnam is a key domino and must be bolstered. So, too, Myanmar, South Korea and some other states, with Japan and India bookending the Indo-Pacific. Developments in the past two years in each of these countries suggest Mr Obama's pivot or rebalance to Asia has been fairly successful.
The rapturous reception that Mr Obama received in Hanoi and Ho Chi Minh City - people even lined up in the rain - underscores American soft power. It contrasted with the muted welcome for Chinese President Xi Jinping last year when even the applause in the Vietnamese Parliament was perfunctory. That is how badly China has messed up its ties with key neighbours.
Vietnam-US ties are set to boom. The tripod on which power in Vietnam resides - the president, prime minister and the Communist Party chief - are all aligned on the US account.
It also helps that the US is showing a willingness to look the other way on some key concerns, notably human rights and government corruption, to pursue its strategic agenda.