Secretary of State John Kerry extolled "diplomacy's power" in January when Iran freed several imprisoned Americans, including Washington Post reporter Jason Rezaian. But was it the power of diplomacy that cinched the release — or was it the might of $400 million in cash?

Brief background: In January, the U.S. dispatched a cargo plane loaded with $400 million in foreign currency to Iran, the Wall Street Journal reports. This happened just as the Iranian nuclear deal with the West kicked in and economic sanctions lifted. The payment was portrayed by the U.S. as a partial settlement in a decades-old Iranian claim over a soured deal to buy U.S. military equipment.

But the timing of the payment prompted senior Justice Department officials to object, according to the Journal. "People knew what it was going to look like, and there was concern the Iranians probably did consider it a ransom payment," one official told the paper.

That's exactly how senior Iranian defense officials have reportedly described it publicly since then.

President Obama denies a quid pro quo, citing longstanding policy that the U.S. doesn't pay ransoms. But, Jonathan Tobin writes in Commentary magazine, reality may be different: "Paying ransoms to terrorists or terrorist regimes is a practice that, at least in theory, the U.S. opposes. But like Israeli governments who also talk tough about not negotiating but then agree to lopsided deals, American leaders usually pay up if that is the only way to gain the release of U.S. hostages."

But this deal's done. The money's safely in Tehran, where it may help the mullahs bankroll terrorists around the globe. The recriminations over whether it was or wasn't a ransom payment likely will subside. What remains important:

• Iran took Americans as de facto hostages. They were innocents arrested and held on trumped-up charges; Rezaian was convicted in a secret trial.

• The $400 million that the U.S. paid to help settle the claim or to gain the release — or both — is a pittance compared with the frozen billions released to Iran in the nuclear deal, and the billions more that could flow into Iran's economy as Western companies return there in force.

But Iran isn't satisfied. Iranian Supreme Leader Ayatollah Ali Khamenei is now furiously backpedaling from the deal he once embraced. He accuses the U.S. of "breaching" its pledges and "obstructing and damaging Iran's economic relations with other countries."

Khamenei's gripes aren't new. In April, he demanded that the Obama administration help make Tehran's financial dealings with foreign companies and banks easier by allowing transactions involving dollars in certain circumstances. We argued against that relaxation because Iran hadn't earned any favors from the U.S. It still hasn't.

Today, Iran is struggling to find financing from foreign banks still skeptical about doing business with the repressive regime. Deals for Iran to buy more than 200 jetliners from Boeing and Airbus are up in the air after the U.S. House passed a bill in July aimed at blocking the sales. The price of oil, Iran's lifeblood, is down.

One unfortunate solution to economic doldrums? Iran has taken yet more Americans captive in recent months and demanded the release of another $2 billion.

The new victims include Reza "Robin" Shahini, of San Diego, who went to Iran to visit his ailing mother in May. On July 11, he was arrested on suspicion of crimes against Iran, the Washington Post reports. Two other U.S. citizens and several dual nationals from Britain, Canada and France are also being held, the paper says.

So don't be surprised if the mullahs press their new demands — and take still more Americans prisoner.

They did get the $400 million.