Liu Xiaobo, China’s only Nobel Peace Prize Laureate, has died.

The 61-year-old political prisoner, who was diagnosed with late-stage liver cancer in May, was jailed in 2009 on charges of “inciting subversion against state power” after he helped pen a petition calling for multi-party democracy in the Communist Party-run state.

Despite his terminal condition, the Chinese authorities refused to let him leave the country to seek treatment abroad. On July 13, the Chinese judicial bureau confirmed his death.

In a statement, U.S. Secretary of State Rex Tillerson paid tribute to Liu’s dedication to “the betterment of his country and humankind, and to the pursuit of justice and liberty.” He called on China to release his wife, Liu Xia, from house arrest and let her leave the country.

Liu’s demise has been as contentious as his tireless struggle to bring human-rights and political reform to his 1.3 billon compatriots. Although he was recently granted medical parole, and moved from prison to a hospital in the northeastern city of Shenyang, not to let him seek possibly lifesaving treatment overseas showed “new depths of cruelty,” said Amnesty International.

“Chinese President Xi Jinping has shown astonishing disdain for Liu Xiaobo’s life, from his wrongful imprisonment to his treatment after being transferred to a hospital,” said Sophie Richardson, China director for Human Rights Watch.

Earlier this month, China invited medical experts from the U.S and Germany to treat Liu — not coincidentally just before Xi traveled to Hamburg for a G20 summit — in an apparent bid to ward off international censure.

Liu’s deteriorating condition was the first diplomatic hurdle faced by Terry Branstad, the newly appointed U.S. Ambassador to China under President Donald Trump.

On June 28, just one day after his arrival at the Beijing Embassy, the former Iowa governor, who has personally known Xi since the 1980s, called for Liu’s unconditional release, saying, “We Americans would like to see him have the opportunity for treatment elsewhere, if that could be any of help.”

China’s Foreign Ministry instead warned against making “irresponsible remarks on Chinese internal affairs,” adding that “China is a country with rule of law, where everybody is equal in front of the law.”

Liu Xia, his wife, has remained under house arrest and sequestered from friends and family since he won the 2010 Nobel Peace Prize. She has never been charged with a crime.

A native of China’s northeastern city of Changchun, Liu rose to prominence by helping to lead China’s 1989 Tiananmen Square democracy uprising, which was ruthlessly crushed at a cost of hundreds, possibly thousands, of lives in the streets surrounding the birthplace of the People’s Republic.

Then aged 33, Liu was credited with urging students to leave their encampment instead of facing down the soldiers’ rifles. He was picked up in the resultant crackdown and imprisoned until 1991, when he was freed without charge.

Liu kept speaking out about democracy and human-rights in his role as a university lecturer, continuing his activism and writing books and poetry largely banned in his homeland. In 2008, Liu, who holds a doctorate in Chinese literature, helped draft Charter 08, which called for sweeping reforms including legislative democracy and a new constitution. As a result, he was sentenced to 11 years in prison on Christmas Day 2009.

On July 7, the Chinese medical team charged with treating Liu stopped using cancer-fighting drugs in order not to overwhelm his severely weakened liver, indicating that his end was near.

In a statement posted online, family friend Zeng Jinyan said the inhibitor drug Sorafenib had failed to work on Liu, citing information received from Liu’s brother-in-law, Liu Hui.

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Write to Charlie Campbell at charlie.campbell@time.com.