August 23 is called Black Ribbon Day. It reminds us of the horrors inflicted on the world by the twin evils of Nazism and communism.

On that date in 1939, the Soviet Union and Nazi Germany inked the Molotov-Ribbentrop Pact. Never again would the two powers threaten one another.

It was a colossal diplomatic blunder. The Soviets thought they could do business with Hitler, that he was doing them a favor. But deals with the devil seldom turn out well. In 1941, Nazi Germany invaded Russia.

Today, another devilish regime is about to offer President Obama a deal. Odds are the White House will take the bargain.

Washington today is buzzing with the notion that it’s time to talk to Tehran. Iran has a newly elected leader, some argue, and the U.S. just might be able to work with him. Moreover, they continue, America has nothing to lose by trying. It’s a happy thought, but wrong on both counts.

While Iran has a new president, it’s the same old regime. And the primary diplomatic goal of Tehran’s leadership—to break through the economic sanctions that are undermining its economic viability—remains unchanged.

Moreover, there is no evidence that the regime has any interest at all in giving up its ambition to become a nuclear power. So how will Tehran seduce Obama into cutting a deal? Read on.

Unlike the former president of Iran, Hassan Rouhani doesn’t care much about being cheered by Third World dictators in Latin America and Africa. He recognizes these relationships are peripheral to the country’s interests. By lowering the level of engagement with these foreign strongmen, he will seem less antagonistic to the West.

Rouhani also couldn’t care less about the Palestinians. Tempering his predecessor’s rooting for Hamas and refraining from threatening to burn Israel to the ground will also make Iran seem more reasonable.

At the same time, Tehran can afford to slow walk its weapons program. They already have bomb designs. And they already have enough low-enriched uranium to build several bombs if further enriched to weapons-grade levels.

What they really need to work on are their delivery systems, the missiles. So while they work on their delivery, they can pretend to be accommodating on the uranium front.

Finally, the “ask” won’t be too big. Iran doesn’t have to press the U.S. to lift sanctions. Tehran just has to get us to stand by quietly while it presses Germany to lead the Europeans in backing off sanctions.

Iran also has a couple of carrots to offer Washington. First, Obama desperately wants to “go to zero” in Afghanistan, pulling out all U.S. troops. Tehran, which has influence in the country, will promise to help to pave the way for America’s exit.

Second, the White House has had few recent foreign policy success and lots of controversy—from the Benghazi debacle to the Russian rebuff to the dithering over Egypt. Anything that looks like a win will help the administration’s Image on the international scene.

But if Obama signs onto Tehran’s terms, he’ll make out no better than Molotov did with Hitler. After slipping the sanctions that have weakened it, the regime will proceed to tighten its control over the Iranian people.

It will continue to be a state sponsor of terrorism. It will one day “surprise” the world and detonate a nuclear weapon. And the next day, the new nuclear arms race in the Middle East will begin in earnest.

The upshot, then, will be a far more dangerous world. Such are the wages when dealing with the devil.

- James Jay Carafano, a Washington Examiner columnist, is Vice President for Defense and Foreign Policy Studies at the Heritage Foundation.