World leaders and celebrities paid tribute to former Soviet leader Mikhail Gorbachev for changing "the course of history" by ending the Cold War following his death on Tuesday night at the age of 91.
Russian President Vladimir Putin took half a day to issue a statement on Gorbachev's death, with a backhanded half compliment on his place in history.
He said that Gorbachev was "a politician and statesman who had a huge impact on the course of world history".
"He deeply understood that reforms were necessary, he strove to offer his own solutions to urgent problems," he said.
The two men were reported to mistrust each other.
Mr Putin blamed Gorbachev for the collapse of the Soviet Union. Gorbachev considered Mr Putin's invasion of Ukraine in February a betrayal.
Boris Johnson said the Kremlin is "intent on undoing the good" of Gorbachev and attempting to "recreate that Soviet empire" with its war in Ukraine, as he paid tribute to the former leader on Tuesday night.
The Prime Minister said: "Mikhail Gorbachev is one of those people who changed the world and unquestionably changed it for the better. When you look at what he did to make Europe whole, free, to give freedom to the countries of the former Soviet Union - it was quite an extraordinary thing.
"And what I worry about today is that the current leadership in Moscow is intent on undoing the good of Mikhail Gorbachev, and is intent on a revanchist attempt, a revenge-driven attempt, to recreate that Soviet empire, and you're seeing that in Ukraine - that's the tragedy, something that Mikhail Gorbachev would have thought was absolutely unthinkable, unwarranted."
I'm saddened to hear of the death of Gorbachev.
I always admired the courage & integrity he showed in bringing the Cold War to a peaceful conclusion.
In a time of Putin's aggression in Ukraine, his tireless commitment to opening up Soviet society remains an example to us all.
Joe Biden hailed Gorbachev's reforms as "the acts of a rare leader" who had "the imagination to see that a different future was possible and the courage to risk his entire career to achieve it."
Gorbachev, Mr Biden said, helped to forge a "safer world and greater freedom for millions of people".
Irish premier Micheal Martin said: "I am deeply saddened to hear of the passing of Mikhail Gorbachev, one of the most significant political figures of the late 20th century.
"At a time when the threat to the world of nuclear destruction was very real, he saw the urgent need for rapprochement with the West and for greater openness and reform - glasnost and perestroika - in the then Soviet Union.
"His leadership helped to end the arms race between the East and West, end the Cold War and bring down the Iron Curtain that had divided Europe since the Second World War."
Conservative leadership contender Rishi Sunak said the legacy of Gorbachev will be "remembered by us all".
Mr Sunak tweeted on Wednesday: "Gorbachev's courage and vision helped bring peace to Europe and built a freer, more open society for millions. His legacy will be remembered by us all."
Labour leader Sir Keir Starmer said Gorbachev was "one of the great figures" of the last century who will "forever be remembered".
The comments were echoed by the president of the European Commission, Ursula von der Leyen, who said Gorbachev's legacy is "one we will not forget".
She said: "It opened the way for a free Europe. This legacy is one we will not forget. R.I.P Mikhail Gorbachev."
French President Emmanuel Macron added: "My condolences for the death of Mikhail Gorbachev, a man of peace whose choices opened up a path of liberty for Russians. His commitment to peace in Europe changed our shared history".
Former German chancellor Angela Merkel paid tribute to Gorbachev as a "unique world politician" who demonstrated how "one single statesman can change the world for the better".
"The images of his meeting with (West German) chancellor Helmut Kohl in the Caucasus in 1990 are unforgettable, with which Germany reunification in peace and freedom also came within reach," said Merkel, who grew up in East Germany.
"Mikhail Gorbachev also fundamentally changed my life. I will never forget that."
Antonio Guterres, the UN Secretary-General, said Gorbachev was "a one-of-a kind statesman who changed the course of history".
"He did more than any other individual to bring about the peaceful end of the Cold War," Mr Guterres said.
Jacinda Ardern, New Zealand's prime minister, said "there is no question he holds an important place in the world's history".
"Gorbachev demonstrated the importance of engagement and diplomacy, shown by the role he played in bringing an end to the Cold War."
Italian Prime Minister Mario Draghi praised Gorbachev for his opposition to "an imperialist vision of Russia".
"His desire for peace, his opposition to an imperialist vision of Russia won him the Nobel prize. These messages are all the more relevant in the face of the tragedy of the invasion of Ukraine," Draghi said in a statement.
Russian winner of last year's Nobel Peace Prize, Dmitry Muratov hailed fellow Nobel peace laureate Gorbachev.
Gorbachev "loved a woman more than his work, put human rights above the state, and valued a peaceful sky more than personal power," Muratov said in a tribute published by leading independent newspaper Novaya Gazeta, which Gorbachev helped set up with part of his Nobel winnings.
BBC presenter and author John Simpson, who interviewed Gorbachev, described the former Soviet president as "a decent, well-intentioned, principled man".
He said: "In private he was charming and surprisingly amusing. It wasn't his fault things went so wrong."
The death of Gorbachev, who was Soviet leader between 1985 and 1991, was reported by the Russian news agency RIA Novosti.
The news agency said that Gorbachev had died of a "serious and prolonged illness" at the Central Clinic Hospital.
Gorbachev was said to be gravely ill earlier this year with a kidney ailment.
Loved by the West and despised by hardliners within the Soviet Union's Communist Party, Gorbachev is credited with helping to end the Cold War and presiding over the collapse of the Soviet Union.
In 1990, Gorbachev won the Nobel Peace Prize "for the leading role he played in the radical changes in East-West relations".
The charming and modernising Gorbachev was voted in as Communist Party General Secretary in 1985, the de facto leader of the Soviet Union when its leadership had been in disarray since the death of Leonid Brezhnev in 1982.
He was the architect of freedoms for many people living in the Soviet Union but also relaxed the control of the authorities, and has been blamed for breaking the Communist system that Vladimir Lenin set up after the 1917 Bolshevik Revolution.
The Soviet Union that he tried to breathe new life into with his liberal reforms, Perestroika and Glasnost, creaked and broke in 1991. It splintered into several new or reborn countries, sparking a sharp economic decline that set off nationalism in across the region and allowed the oligarchs to grab.
Gorbachev was the target of a failed hardline coup and by the end of 1991 he had resigned in favour of the ascending Boris Yeltsin.
Gorbachev and Vladimir Putin, Russia's president, were reported to mistrust each other. Gorbachev considered Mr Putin's aggression toward former Soviet states, his invasion of Georgia in 2008 and his invasion of Ukraine in February as betrayals.
Mr Putin blamed Gorbachev for the collapse of the Soviet Union, which he has made rebuilding the focus of his presidency.
There has, so far, been no reaction to news of Gorbachev's death from the Kremlin but pro-war and pro-Kremlin channels have rejoiced, calling him a "traitor".
Gorbachev described his friendly relationship with Margaret Thatcher as a catalyst for the tearing down of the Iron Curtain.
"We gradually developed personal relations that became increasingly friendly," he said following her death in 2013.
"In the end, we were able to achieve mutual understanding, and this contributed to a change in the atmosphere between our country and the West and to the end of the Cold War."
The former Soviet leader met the Prime Minister in 1984, when he led a Russian parliamentary delegation to Britain.
After that meeting, Mrs Thatcher said of Gorbachev: "We can do business together".
Gorbachev conceded that the relationship was "not always smooth" but said they "stayed in touch, exchanging letters" over the years.
Gorbachev did not appear to have the same respect for Reagan. Declassified documents show that after the US-Soviet summit at Reykjavik in 1986, Gorbachev complained of Reagan's "extreme primitivism, a caveman cast of mind and intellectual feebleness".
Mrs Thatcher was an important interloper between the two men - "an agent of influence in both directions" - as her former foreign policy adviser Sir Percy Cradock put it.
Gorbachev was known to enjoy holding vigorous debates with Mrs Thatcher and valued her attention to detail and ability to work long hours with little sleep, traits they shared.
Tom Tugendhat, the chair of the Commons foreign affairs select committee, wrote on Twitter. "Mikhail Gorbachev's reported death... is a reminder of how far Russia has fallen. From a powerful, if tyrannical state to now the playpen of gangsters and war criminals."
Some online tributes offered a lighthearted salute to another memorable moment in Gorbachev's life: an advert for Pizza Hut.
The US restaurant chain opened in Moscow in 1990.
The 1998 advert features Gorbachev sitting in the restaurant while a family at another table debate Gorbachev's political legacy.
Mikhail Gorbachev, the last leader of the Soviet Union, has died, per AFP.
He allowed companies like Pizza Hut to enter into Russia, and thus one of the greatest commercials of all time was created.
RIP: pic.twitter.com/Hpqs2sxtWe
The family matriarch concludes that Gorbachev has given Russia "many things" - including Pizza Hut.
One Twitter user wrote: "This Mikhail Gorbachev Pizza Hut commercial is what historians will someday say marked the real end of the cold war and is a masterpiece."
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