What the WikiLeaks documents tell us about the practice of foreign policy.

The main thing about the latest trove of secret WikiLeaks documents is this: It exists, it's out there for the world to see, and it would be regardless of whether the editors of the New York Times, Le Monde, the Guardian, Der Spiegel, and El País chose to print the news (and much of this trove is newsworthy) or shut their eyes.

So let's pretend for a moment that WikiLeaks' founder, Julian Assange, was motivated not by a messianic, anti-American, cyberanarchistic glee ("I enjoy crushing bastards," he once told an interviewer) but by a desire to show us how the world really works.

Beyond the questions surrounding the massive nature of their disclosure—right or wrong, catastrophic or merely embarrassing—what do these documents reveal about U.S. foreign policy and the nature of diplomacy?

Mainly they illustrate principles about the "great game" of power politics dating back to Thucydides—that nations behave according to their material interests and that a big part of diplomacy lies in appealing to, threatening, or manipulating those interests.

And they show that, within the narrowing realm in which the United States (or any country) can influence others in the post-Cold War world, the Obama administration has been playing the game fairly well.

Take the section of the new WikiLeaks documents dealing with President Barack Obama's attempts to rein in Iran's nuclear program (in many ways the most interesting section released so far).

Conservative critics have portrayed President Barack Obama as an international naif who relies excessively (or even exclusively) on accommodation and engagement. However, the documents show him, in his first few months in the White House, maneuvering to tighten and broaden the scope of economic sanctions.

George W. Bush had also tried to rally a worldwide sanctions campaign, but he faced roadblocks from Russia and China, whose participation was vital to any such effort's success. Both countries had strong trade ties to Iran. (China imported nearly one-eighth of its oil from Iran.) So, the documents show, Obama set out to pry loose those ties or to offer rewards for untangling them.

In the case of China, Obama dispatched Dennis Ross, a White House adviser who had been the Middle East negotiator for Presidents Bill Clinton and George H.W. Bush (but who had no post in his son's administration), to persuade Saudi Arabia to guarantee that it would supply oil to the Chinese if Iran cut them off. As a result of that assurance, China signed up for sanctions.

In the case of the Russians, Obama placated their distress over Bush's plan to install missile-defense systems on Eastern European soil by canceling the plan. As a result of that move, which triggered a whole "re-setting" of relations between Moscow and Washington, Russia joined the sanctions as well. (Obama didn't abandon missile defenses; he only relocated the interceptors onto ships, which had the additional benefit of clarifying that they really were aimed to shoot down Iranian missiles, not Russian ones.)