The United States and Iran have suddenly announced a prisoner swap, and each freed a prisoner on 7 December.

The swap was facilitated by Switzerland. After four weeks of intensive negotiations, the US released Iranian stem cell expert Massoud Soleimani in exchange for Xiyue Wang, a Chinese-American detained in Iran for three years on espionage charges. Iran’s Foreign Minister Javad Zarif tweeted a picture of him and Soleimani flying back to Iran.

Soleimani was arrested at Chicago airport in 2018 for attempting to export biological materials to Iran, which was a violation on US sanctions over Iran’s nuclear program.

Xiyue Wang was detained in 2016 while he was doing a dissertation research in Iran, under the accusation of “spying under the cover of research”.

US President Donald Trump thanked Iran for the “very fair negotiation”:

“Freeing Americans held captive is of vital importance to my administration, and we will continue to work hard to bring home all our citizens wrongfully held captive overseas,” Trump said.

In 2018, Trump withdrew from a 2015 nuclear agreement between Iran and world powers, and reimposed economic sanctions on Iran, which further raised tensions between the two sides.