Ten years after the United States evacuation from Vietnam, Hanoi has found itself in the slightly uncomfortable position of being a stumbling block on Moscow's path to reconciliation with Peking. But Vietnam has proved its ability to use its military might, which Moscow helped it build during the war, against Chinese troops and has shown the power and will to impose its wishes on a large part of Indochina.
Under present circumstances Moscow's close ties with Hanoi allow the Kremlin a large measure of influence over both Kampuchea (Cambodia) and Laos, whose Vietnamese-backed governments are treated as allies when their leaders visit Moscow.
Peking has said Soviet pressure on Hanoi to withdraw its troops from Kampuchea would be appreciated as at least a gesture toward Chinese feeling and a hint of some readiness to compromise in the interest of Sino-Soviet relations.
The Kremlin maintains publicly that no third country has any bearing on Moscow-Peking relations. But Vietnam's recent moves to reduce its military presence in Kampuchea have clearly taken place following consultation with the Soviets.
Vietnamese Vice-President Nguyen Huu Tho arrived in Moscow last Monday for ``routine consultations,'' but Moscow-based Sinologists noted the significance of the timing: He arrived on the same day that Chinese Deputy Foreign Minister Qian Qichen left the Soviet capital after the latest round of talks between the two communist giants on improving their relations.
Hanoi is following closely the process of improving Sino-Soviet ties and pushing its right to a thorough briefing from the Kremlin at every phase.
Vietnamese Foreign Minister Nguyen Co Thach is a regular Kremlin visitor. Particularly since the resumption of Sino-Soviet dialogue in 1982, Mr. Thach has made a point of flying to Moscow about once a year for discussions with Soviet Foreign Minister Andrei Gromyko.
Meanwhile, Soviet trade with Hanoi rises steadily, from turnover worth about $1 billion in 1981 to just over $1.4 billion last year, most of it in Soviet exports.
Vietnam's involvement in Kampuchea, Soviet troop levels in Mongolia and Moscow's invasion of Afghanistan are the three primary obstacles cited by Peking to restoring good relations.
The comparison between US involvement in Vietnam and Moscow's present entanglement in Afghanistan is one that is strictly avoided in the Soviet Union.
The US war in Vietnam is described as proof of the aggressive intentions of capitalism.
The official Soviet press invariably responds to US allegations that Soviet troops have used chemical warfare in Afghanistan with commentaries on the fateful consquences of US use of Agent Orange, a defoliant, in Vietnam.
References to the chemical's long-term side effects on crops and people are, however, notably absent when Soviet shops proudly boast that their normally meager supplies of exotic goods are supplemented by canned Vietnamese pineapples.