Military leaders in Syria, Iraq and Russia claimed a decisive victory over Islamic State last year, but western officials say the declaration is premature. Analysts also warn that further insurgencies are likely.
Three years after the group captured swathes of territory in Syria and Iraq, creating a caliphate that ruled over millions of people, The Week looks at whether the war against IS has finally been won.
What are the regional leaders saying?
The Russian military, which has been fighting alongside Syrian President Bashar al-Assad's troops since 2015, claims "all formations" of the terrorist group have been defeated in the country.
Announcing plans to partially withdraw his troops from the war-torn nation last month, Russian President Vladimir Putin said: "In two years, the Russian armed forces, together with the Syrian army, have defeated the most lethal group of international terrorists."
His declaration of victory came a month after Assad's army celebrated the collapse of the group's self-styled caliphate when it recaptured Albu Kamal, one of the last towns held by the jihadists in Syria.
Across the border in Iraq, the military and Kurdish Peshmerga forces also claim to have "fully liberated" all territory from the terrorist group, including the full length of the Iraqi-Syrian frontier.
But Iraq's Prime Minister, Haider al-Abadi, warns that driving the militants from the country will not eliminate the threat.
IS is "very dangerous and if given any chance they will return", the prime minister said.
What about western officials?
The US military, which has been leading the international coalition against IS since 2014, has expressed scepticism at the claims of "total victory". In November, the Pentagon warned that the war was not over and claimed that thousands of fighters were still active in the region, according to The Times.
While acknowledging that progress has been made, Britain has also stopped short of declaring the demise of the group. The recapturing of territory in Iraq "signals a new chapter towards a more peaceful, prosperous country," Theresa May said last month.
"We must be clear however, that whilst Daesh (IS) is failing, they are not yet defeated," she said. "They still pose a threat to Iraq, including from over the Syrian border."
How much territory has Islamic State lost?
At its peak, the group controlled nearly a third of Iraq and more than a quarter of Syria, an area roughly the size of Britain with a population of 10 million. The vast territory, stretching from Syria's northeast to deep inside Iraq, included oil fields, which provided IS with a vital source of income.
But since 2014, the group has lost more than 90% of the territory it once controlled in the two states. Its biggest losses occurred last year when Iraq's second largest city -- Mosul -- was liberated from the jihadists. Three months later, Raqqa, its operational capital in Syria, finally fell.
Pockets of resistance remain in Syria, but the jihadists now hold just a small stretch of towns running south along the Euphrates River and into Iraq, the Washington Post says.
What about its funding and fighters?
As well as revenue from black market oil sales, IS relies on taxation, extortion, asset raids and income from foreign donors to fund its military offensives. After seizing the central bank of Mosul in 2014, the militants had an estimated $2bn (£1.5) in assets, according to figures obtained by Al Jazeera.
Since then, its revenue stream has plummeted from a monthly average of $81m (£60m) in the second quarter of 2015 to $16m (£11.2m) in the same period of 2017, according to IHS Markit analysis quoted by Newsweek.
The group's money flow has "dried up and its stream of volunteers has dwindled to a trickle," says Daniel Byman, a senior fellow at the Center for Middle East Policy at the Brookings Institution. "Many of its fighters, who the group once boasted would battle to the death, have surrendered or fled," he said.
Yet IS has a proven track record as an insurgency able to withstand major military onslaughts, while still recruiting fighters around the world ready to kill in its name, the New York Times reports.
IS leaders "signalled more than a year ago that they had drawn up contingency plans to revert to their roots as a guerrilla force after the loss of their territory in Iraq and Syria," the paper adds.
"Nor does the group need to govern cities to inspire so-called lone wolf terrorist attacks abroad, a strategy it has already adopted to devastating effect in Manchester and Orlando."
Jason Burke, a journalist and the author of The New Threat: The Past, Present and Future of Islamic Militancy, agrees that further insurgencies are likely as the extremists are pushed underground.
This is because the recent military offensive has not been accompanied by a parallel political effort, he argues in The Guardian.
"There are still deep wells of resentment and fear among Iraqi Sunnis, and the Syrian civil war grinds on," Burke says. "The project of constructing an Islamic state has been defeated, but the organisation has not."
Who is right?
Military leaders are correct in claiming that the Islamic caliphate has collapsed, crushing the group's claim to statehood. Despite this, its powerful ideology lives on, raising the spectre of a new wave of insurgencies in the region, as well as deadly terrorist attacks abroad.