So-called Islamic State (IS) lost almost a quarter of its territory in 2016, according to new analysis.
The group gave up almost 18,000 sq km (6,900 sq miles), its territory being reduced to some 60,400 sq km, just less than the size of Florida, security and defence analysts IHS Markit reported.
IHS Markit predicted the recapture of Mosul by Iraqi government forces by the middle of the year.
But it said the stronghold of Raqqa would be a tougher nut to crack.
IHS Markit said the 23% reduction in IS-held territory in 2016 followed on from a 14% loss the year before.
“The Islamic State suffered unprecedented territorial losses in 2016, including key areas vital for the group’s governance project,” said Columb Strack, senior analyst and head of the IHS Conflict Monitor.
He said that this came despite IS retaking the city of Palmyra in December, “from a Syrian government preoccupied at the time with Aleppo”.
In Mosul – Iraq’s second city, which has been under the control of the extremists since 2014 – Iraqi government forces had “made steady progress” in eastern districts, the report says, although they have been meeting heavy resistance in recent days.
Mr Strack said: “We expect Iraqi government forces to recapture Mosul before the second half of the year.
“After Mosul, the Iraqi government will probably focus its attention on the remaining pocket of resistance around Hawija, which the jihadists are using as a base for their campaign of sustained terrorist attacks in Baghdad.”
Taking Raqqa would be more difficult “given the complex political and military considerations involved”, the IHS Conflict Monitor report said.
Raqqa is regarded as the “capital” of the self-declared IS caliphate.
In November, a US-backed coalition of Kurdish and Arab fighters, the Syria Democratic Forces (SDF), said it had begun an operation to capture Raqqa.
But progress had “stalled in the triangle between the Euphrates and the Balikh river”, the report said.
“Raqqa represents the core of the Islamic State and they are unlikely to leave without a fight,” Mr Strack said. Capturing it would “probably take a major ground intervention by one of the main external players”.
The report also highlighted what it said was a major theological dispute within IS, between those following mainstream doctrine and those taking a more extreme interpretation.
This could raise the risk of defections or even cause an internal break-up, IHS Conflict Monitor said.