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This was the justification for increasing engagement with Iran, notably the Obama-era nuclear deal. It was thought - or at least said - that Iran could be turned into a meaningful collaborator, almost a partner.

President Barack Obama and his diplomats worked hard in pursuit of this rosy picture - both initially, though unsuccessfully, in an attempt to bring it about, and later to convince onlookers that it was still accurate.

The assumption that Iran could be induced to moderation was incorrect. It was axiomatically wrong. The spirit of the 1979 revolution remains strong and dictates more than a way of seeing the world; it shapes the nation, dictating domestic politics and Iran's actions on the world stage.

This is not a pose or posture. It is fundamental to the Iranian state.

Essential features of Iran's politics cannot be removed or reformed - at least not by dialogue alone. This includes Iran's theocratic leadership, its managed democracy, its consistent support for international terrorist organisations, its propping up and increasingly taking over the barbarous regime of Bashar al-Assad.

The behaviour of the Iranian state cannot be brought into line by inducements, as was repeatedly proven to Obama.

Iran has done this before and Wang is not the only American in Iranian prisons

One of the final and defining images of the Obama administration's relationship with Iran was not a conference room, or the sombre but dignified marking of an agreement reached. It had little to do with the nuclear deal.

Instead, it was the image of American sailors briefly detained by Iranian ships, and the gloating of Iranian authorities.

America looked weak - that was the rallying cry of the Republican right wing. But it should not have been a surprise. Such things can and do happen between states as strained as Iran and the US.

And such things will continue to happen regardless of who is president, as is demonstrated by the case of , a postgraduate researcher at Princeton, who has been jailed by Iran on spying charges for 10 years. No doubt the charges are trumped up.

The reasons for his detention have been speculated upon at length. Some of his academic work involved the use of Iranian archives. Bizarrely, this is cited as the pretext for his detention, to Mizan. Wang was "infiltrating Iran's national archive and building a 4,500-page digital archive" to pass on to the American government, the Harvard Kennedy School and other assorted enemies.

Of course, this is absurdity.

This imprisonment is very possibly an attempt to send a message by exerting power over something even reduced states can corral and intimidate: Individuals, in this case the adversary's own citizens.

Iran has done this before and Wang is not the only American in Iranian prisons.

Prominent Americans held prisoner in Iran include Siamak Namazi and his father, Baquer. There are others. Robert Levinson is believed to be in Iranian custody after going missing ten years ago.

Iran is not the first nation to use American citizens as bargaining chips or for propaganda reasons. One cannot but think of Otto Warmbier, detained and then imprisoned by the North Korean state. This example is made all the more pertinent by the terrible treatment Warmbier received, and the fact that, mere days after being returned to America and his family, he died. 

If nothing else, we must remember that hostage-taking is not simply a political game for governments. It is a deeply cruel practice which victimises individuals precisely because they, unlike governments, have no way to counter the oppressively deployed force of state power.

Iranian hostage-taking is consistent and long-established. When Iran is treated with leniency, as it was by the Obama administration, it still retained American prisoners.

Iran is not the first nation to use American citizens as bargaining chips and for propaganda reasons

Donald Trump's policy towards Iran has been notably tougher - necessarily so in Syria, where American forces have directly attacked Iranian proxies attempting to assault a base at al-Tanf manned by US-supported Syrian opposition fighters and by American and British special forces.

But the Trump administration, though it has addressed the wider issue of Americans held prisoner in Iran, has had little success in bringing their incarceration to an end.

Meetings have been held. But nothing has been agreed. The Iranian imprisonment of Wang ups the ante, and makes things more uncomfortable for the US at minimal cost.

Partly, this failure is due to the posture of the new administration. Trump talked tough on Iran during the election campaign. Its regime was one of the few non-democratic governments he did not find it in him to praise. But the motivation for that posture came from Obama's perceived weakness.

The motivation for Trump's tough talking on Iran came from a perceived weakness in Obama

It's far harder to look tough in negotiations over Americans held in Iran. The rewards for success are limited compared with the humiliation risked by the possibility of failure.

This is the limitation of Trump's image-conscious policy - just as Obama's obsession with image meant concluding a deal, any deal, with Iran over nuclear weapons was so vital.

President Trump's policy on Iran is backed up with the right words and, indeed, with the threat of a military response when the latter transgresses. Threatening American troops in an American-maintained base is unacceptable, so this is an appropriate strategy.

But what is also needed is a broader approach, which deals with such obvious provocations as Iranian aggression towards American-trained Syrian rebels and Iranian-sponsored war crimes in Syria while also agitating on behalf of all US prisoners in Iran, rather than simply reacting to those who make the president look weak and left at the mercy of events.

On this issue there is a consensus briefly created. The horror of Warmbier's fate at the hands of the North Koreans has raised state hostage-taking in the collective consciousness. As part of a more consistent policy designed to arrest Iranian excesses in Syria, America must look within Iran's borders, to the Americans trapped within. And it must do all it can to help them escape their terrible imprisonment.

James Snell is a writer and blogger whose work has appeared in National Review, Prospect, CapX, NOW News, Middle East Eye, History Today and Left Foot Forward - among others. 

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Opinions expressed in this article remain those of the author and do not necessarily represent those of °®Âþµº, its editorial board or staff.