Direct diplomatic outreach to America's foes and rivals defines President Obama's foreign policy. It underpins everything from "resetting" relations with Russia to making concessions to Iran. It's intended to distinguish Mr. Obama from his unpopular predecessor, thereby garnering more support from friends and allies for U.S. policies.

The idea is appealing. Even Winston Churchill reportedly said "it's better to jaw-jaw than to war-war."

But the approach carries a mixed historical record. As with so many well-meaning gestures, it can result in things going horribly wrong.

A classic example is John F. Kennedy's early overtures to Soviet Premier Nikita Khrushchev. An inexperienced and overly eager Kennedy invited Khrushchev to a summit in Vienna, Austria, in June 1961, suggesting through back channels that he could compromise on nuclear testing if Khrushchev made it appear to be a Soviet suggestion. The move didn't work.

The summit ended miserably. Khrushchev "just beat [the] hell out of me," Kennedy said. Having sized up the young president, Khrushchev two months later bucked the West, erected the Berlin Wall and restarted nuclear weapons testing.

The story continued. A year later, surveillance flights found Khrushchev putting missiles in Cuba, apparently calculating that Kennedy would not respond forcefully. He was wrong. Kennedy publicly exposed the missile installations on Oct. 22, 1962. A missile attack from Cuba, JFK announced, would be seen as an attack by the Soviet Union, and the U.S. would respond accordingly.

It had been a dangerous double miscalculation: Kennedy wrongly believed that "reaching out" would make Khrushchev more conciliatory, while Khrushchev read Kennedy's friendliness as weakness. Both were guilty of projection - believing the other thought just like he did. Like American liberals today, Kennedy incorrectly thought sophistication and good will could charm our foes. Meanwhile, the wily, cynical Khrushchev thought the perceived missile gap would leave Kennedy weak-kneed.

Both were mistaken. And by acting on those erroneous assumptions, they brought the world to the brink of nuclear war.

President Carter's outreach to the Soviet Union provides another example. Six days after his inauguration, he wrote Leonid Brezhnev, the Communist Party's general secretary and de facto Soviet leader, assuring him that the U.S. didn't seek military superiority. He proposed an early summit to hammer out a quick strategic arms limitation and nuclear test ban agreement.

In his quest for disarmament, Mr. Carter canceled the U.S. neutron bomb and B-1 strategic bomber programs. His obsession with arms control helped convince the Soviets that he would not respond to an invasion of Afghanistan, and they went ahead and did so in December 1979. (For the record, President Reagan restored the neutron bomb development and B-1 production in 1981, shortly after assuming office.)

In these cases, U.S. leaders misunderstood how their foes would interpret their friendly overtures. How could their good will go unreciprocated?

Their assumption was not so much naivete as an ideologically induced idea that others' grievances against the U.S. are partially justified; remove the grievances and they'd come around. Little weight was given to the fact that countries challenge us for reasons of power and interest, not simply because they are upset with our treatment of them.

These examples should serve as cautionary tales. Mr. Obama appears deeply committed to the notion that many of America's problems in the world arise from President George W. Bush's lack of direct diplomatic engagement. Reaching out to Iran, Russia and Muslims is predicated on this idea, which is more an ideological default position than a pragmatic plan for correcting past mistakes.

If Mr. Obama adheres to this belief too rigidly, he will lose sight of the same realities that wound up biting the Kennedy and Carter presidencies.

The biggest danger is with Iran. Mr. Obama's repeated overtures could easily lead Tehran to conclude that the U.S. would never use force to stop its nuclear program. Iran discloses a secret nuclear enrichment site, and the U.S. responds with not only an overture for direct talks but also with a concession on certain types of enrichment. Tehran cracks down on opposition groups after fraudulent presidential elections, and Mr. Obama is slow to condemn - another sign the U.S. wouldn't respond forcefully to Iran's transgressions.

Ironically, this approach most likely will encourage Iran to act in more destabilizing ways, possibly until it pushes the administration past its breaking point. In the Iranian hostage crisis, Mr. Carter initially ruled out use of force, but ultimately, he was forced to reverse course. Mr. Carter's failures were the result of diplomatic confusion born from good intentions.

Mr. Obama's conciliatory gestures and apparent resistance to the use of force could embolden the Iranian regime to challenge us further. And that could provoke a desperate reaction from the Israelis. Should Tel Aviv feel abandoned by the White House, it may decide its only option is to take matters into its own hands.

Preconceived notions can blur understanding of our opponents' motivations. The miscalculations allow ideology, rampant in internal political debates, to trump realistic assessments of facts on the ground.

Bottom line? Mr. President, be careful about what you think you know about those folks sitting across the diplomatic table.

Kim Holmes is vice president of foreign- and defense-policy studies at the Heritage Foundation and author of "Liberty's Best Hope: American Leadership for the 21st Century."