William Cohen this week became the first U.S. defense secretary to visit Vietnam since Melvin Laird went in 1971 to begin planning the American military withdrawal. Secretary Cohen is right to insist that this long overdue and necessary mission is about forging a future, not dwelling on the past.

But clearly, a future relationship of trust and cooperation between the United States and Vietnam depends upon the extent to which the two nations reconcile the past they share. It is for that reason that Secretary Cohen spent much of his first day there in a rice paddy south of Hanoi, watching several hundred Vietnamese workers sift through the mud for the remains of a Navy pilot shot down in 1967.

It is also for that reason that two of the major agenda items are accounting for the missing in action — 2,000 Americans, some 300,000 Vietnamese — and the acceleration of a joint effort to rid the countryside of the hundreds of thousands, perhaps millions, of landmines that still make daily life a terror. It is even possible that the increased sharing of medical information will lead to a breakthrough in the treatment of those, Americans and Vietnamese alike, who were exposed to the defoliant Agent Orange.

Only the successful resolution of these issues of the past, or at least good-faith efforts to resolve them, can make the future envisioned by Secretary Cohen possible — a future in which Vietnam and the other members of ASEAN, the Association of Southeast Asian Nations, use their collective “leverage” to deal with the regional superpower, China. The United States’s human-rights and trade issues regarding China are important. So are ASEAN’s worries about China’s territorial designs upon several islands in the South China Sea. China cannot be intimidated, but China can be made to realize that concerns about its conduct are not confined to the West.

The recent history of the United States and China is a confusing combination of confrontation and conciliation, with Vietnam often caught in the middle. In 1979, just four years after China helped North Vietnam conquer the South, the two allies went to war in a dispute over Cambodia. In 1994, China revived diplomatic relations with Vietnam, but the real-world relations have remained icy. The United States revived its diplomatic relations with Vietnam a year later — the follow-up has been equally glacial.

It has been 25 years since the fall of Saigon and the rise of Ho Chi Minh City. Vietnam remains unrebuilt and desperately poor. The entire region remains unstable and in danger of being dominated by China. Secretary Cohen’s brief visit alone will not change these things, but its focus upon human side of the aftermath of war is the only place to start.