Today we celebrate the freedom of one of the American hostages held on trumped-up charges by the Islamic republic of Iran. Xiyue Wang, a Princeton graduate student, has been released in exchange for an Iranian biology professor jailed on sanctions-related charges.

But the happiness for Wang and his family will be tempered by the knowledge that Tehran is still holding several U.S. citizens, as part of its continuing, 40-year-long habit of taking foreign nationals hostage, despite diminishing returns.

Wang, who was in Tehran on a valid visa with funding from Princeton to do historical research for his doctorate, was arrested in August 2016 is finally coming home.

The prisoner exchange that secured his release was negotiated by U.S. and Iranian diplomats through official Swiss intermediaries. Since Washington and Tehran broke off ties in 1980, in the absence of direct relations, Switzerland has served as the protecting power for American interests in the Islamic republic. Despite hostilities, both sides consider the Swiss honest brokers and a channel to discuss ongoing prisoner cases remains open all the time, even if activity is sometimes dormant.

This isn’t the first time the two sides have engaged in this sort of trade, but it’s the first during the Trump era, and Wang’s release provides hope that other Americans still being held in Iran unjustly will find their way to freedom soon.

In the meantime, though, we should rejoice in Wang’s return to his wife, Hua Qu, and their 5-year-old son, Shaofan, who was just a toddler the last time he saw his father.

Hua was a tireless advocate for her husband’s freedom. She became more familiar with Iranian politics — specifically its hostage diplomacy — and American bureaucracy than anyone should ever be forced to endure.

It was frustrating, and there was rarely any sign of light at the end of the tunnel, but she persisted in the face of institutional blockades that keep family members of hostages as far away as possible from efforts around securing a release.

She had no way of knowing if officials were being honest with her about progress in her husband’s case, had to continue working while raising a small child alone, and relied on a circle of friends in her community to look after the boy when she would make regular trips to Washington or New York to advocate for her husband privately and at human rights fundraisers and galas where camaraderie among hostage families often begins to take shape.

It’s at these occasions where former hostages, loved ones of hostages who didn’t make it home alive and those who are still waiting for good news bond over a shared set of experiences to which precious few people can relate.

These family advocates steel themselves for the awkwardness of being put on display, knowing that, in some impossible-to-define way, it may help. And sometimes these events are too much to bear.

I recount this because I want Hua to know that we see her, and also to acknowledge how difficult one family’s good news can be for others. We must remember that there are still whole communities waiting for the release of their loved ones from Iran.

This past Tuesday, the Senate Human Rights Caucus organized a discussion with some of them, including relatives of Bob Levinson, Nazanin Zaghari-Ratcliffe, and Siamak and Baquer Namazi, all foreign nationals who for political reasons were abducted by the Iranian regime and are still separated from their loved ones.

Following Wang’s release, the family of Levinson, a former FBI agent who was detained by Iranian authorities in 2007 and is considered the longest-held hostage in U.S. history — issued a bittersweet statement congratulating Wang and his family but also pressing the Trump administration to do more.

“We can’t help but be extremely disappointed that, despite all its efforts, the United States government was unable to secure his release as well, especially after such a painful week for our family,” the statement said. Levinson’s wife, Christine, and seven children testified in federal court on Wednesday in a case the family has brought against Iran’s government. The statement went on: “Iranian authorities continue to play a cruel game with our father’s life, and with our family.”

The Namazi family expressed similar disappointment: “I am beyond devastated that a second President has left my ailing father Baquer Namazi and brother Siamak Namazi behind as American hostages in Iran in a second swap deal,” said Babak Namazi in a statement.

We can’t ignore the suffering inflicted on these innocent families and should acknowledge the many efforts they make, along with friends and employers of people held hostage abroad. Without them, the rights of unjustly detained prisoners are too easily forgotten.

“I hope as a country we’ll remain vigilant on challenging Iran’s bad human rights record and not back off in exchange for a few people being released. But for the individuals who continue to be held in Iranian prisons and whose families are being tormented by this over years, we should not diminish how significant it would be for them,” Sen. Christopher A. Coons (D-Del.) told me after Tuesday’s event.

While we celebrate Wang’s release and hope for freedom for the others very soon, we must change the calculations for the Iranian and other regimes that practice state-sponsored hostage taking. This is a problem that is only getting worse and will require a collective approach to end it once and for all.

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