Five months after US-backed forces ousted Isis from its last shard of territory in Syria, the terrorist group is regaining strength, military and intelligence officers have warned.

Isis is gathering new strength, conducting guerrilla attacks across Iraq and Syria, retooling its financial networks and targeting new recruits at an allied-run tent camp, US and Iraqi officials said.

Though Donald Trump hailed a total defeat of the Islamic State this year, defence officials in the region see things differently, acknowledging that what remains of the terrorist group is here to stay.

A recent inspector general’s report warned that a drawdown this year from 2,000 US forces in Syria to less than half that, ordered by Mr Trump, has meant the US military has had to cut back on its support for Syrian partner forces fighting Isis.

For now, US and international forces can only try to ensure that Isis remains contained and away from urban areas.

Timeline of the Isis caliphate Show all 19 1 /19 Timeline of the Isis caliphate Timeline of the Isis caliphate ISIS began as a group by the merging of extremist organisations ISI and al-Nusra in 2013. Following clashes, Syrian rebels captured the ISIS headquarters in Aleppo in January 2014 (pictured) AFP/Getty Timeline of the Isis caliphate Abu Bakr Al-Baghdadi declared the creation of a caliphate in Mosul on 27 June 2014 Timeline of the Isis caliphate Isis conquered the Kurdish towns of Sinjar and Zumar in August 2014, forcing thousands of civilians to flee their homes. Pictured are a group of Yazidi Kurds who have fled Rex Timeline of the Isis caliphate On September 2 2014 Isis released a video depicting the beheading of US journalist Steven Sotloff. On September 13 they released another video showing the execution of British aid worker David Haines Timeline of the Isis caliphate The US launched its first airstrikes against Isis in Syria on 23 September 2014. Here Lt Gen William C Mayville Jnr speaks about the bombing campaign in the wake of the first strikes Getty Timeline of the Isis caliphate Isis militants sit atop a hill planted with their flag in the Syrian town of Kobani on 6 October 2014. They had been advancing on Kobani since mid-September and by now was in control of the city’s entrance and exit points AFP/Getty Timeline of the Isis caliphate Residents of the border village of Alizar keep guard day and night as they wait in fear of mortar fire from Isis who have occupied the nearby city of Kobani Getty Timeline of the Isis caliphate Smoke rises following a US airstrike on Kobani, 28 October 2014 AFP/Getty Timeline of the Isis caliphate YPG fighters raise a flag as they reclaim Kobani on 26 January 2015 VOA Timeline of the Isis caliphate Isis seized the ancient Syrian city of Palmyra on 20 May 2015. This image show the city from above days after its capture by Isis Getty Timeline of the Isis caliphate Kurdish forces are stationed on a hill above the town of Sinjar as smoke rises following US airstrikes on 12 November 2015 AFP/Getty Timeline of the Isis caliphate Kurdish forces enter Sinjar after seizing it from Isis control on 13 November 2015 AFP/Getty Timeline of the Isis caliphate Iraqi government forces make the victory sign as they retake the city of Fallujah from ISIS on 26 June 2016 Getty Timeline of the Isis caliphate Iraqi forces battle with Isis for the city of Mosul on 30 June 2017 AFP/Getty Timeline of the Isis caliphate Members of the Iraqi federal police raise flags in Mosul on 8 July 2017. On the following day, Iraqi prime minister Haider Al Abadi declares victory over Isis in Mosul Getty Timeline of the Isis caliphate Members of Syrian Democratic Forces celebrate in Al-Naim square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign Getty Timeline of the Isis caliphate Female fighters of the Syrian Democratic Forces celebrate in Al-Naim Square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign AFP/Getty Timeline of the Isis caliphate Trucks full of women and children arrive from the last Isis-held areas in Deir ez-Zor, Syria in January 2019 They were among the last civilians to be living in the ISIS caliphate, by this time reduced to just two small villages in Syria’s Deir ez-Zor Richard Hall/The Independent Timeline of the Isis caliphate Zikia Ibrahim, 28, with her two-year-old son and 8-month-old daughter, after fleeing the Isis caliphate, on Saturday 26 January 2019 Richard Hall/The Independent

Although there is little concern that the Islamic State will reclaim its former physical territory, a caliphate that was once the size of Britain and controlled the lives of up to 12 million people, the terror group has still mobilised as many as 18,000 remaining fighters in Iraq and Syria.

These sleeper cells and strike teams have carried out sniper attacks, ambushes, kidnappings and assassinations against security forces and community leaders.

The Islamic State can still tap a large war chest of as much as $400m (£331m), which either has been hidden in Iraq and Syria or smuggled into neighbouring countries for safekeeping. It is also believed to have invested in businesses, including fish farming, car dealing and cannabis growing. And the group uses extortion to finance clandestine operations. Farmers in northern Iraq who refuse to pay have had their crops burned to the ground.

During the past several months, Islamic State has made inroads into a sprawling tent camp in northeast Syria, and there is no ready plan to deal with the 70,000 people there, including thousands of family members of Isis fighters.

US intelligence officials say the Al Hol camp, managed by Syrian Kurdish allies with little aid or security, is evolving into a hotbed of Islamic State ideology and a huge breeding ground for future terrorists. The US-backed Syrian Kurdish force also holds more than 10,000 Islamic State fighters, including 2,000 foreigners, in separate makeshift prisons.

At Al Hol, the Syrian Kurds’ “inability to provide more than ‘minimal security’ at the camp has allowed the ‘uncontested conditions to spread of Isis ideology’ there,” said the inspector general’s report, which was prepared for the Pentagon, the State Department and the US Agency for International Development.

The military’s Central Command told the report’s authors that “Isis is likely exploiting the lack of security to enlist new members and re-engage members who have left the battlefield.”

A recent United Nations assessment reached the same conclusion, saying that family members living at Al Hol “may come to pose a threat if they are not dealt with appropriately.”

These trends, described by Iraqi, American and other Western intelligence and military officials, and documented in a recent series of government and UN assessments, portray an Islamic State on the rise again, not only in Iraq and Syria, but in branches from West Africa to Sinai.

This resurgence poses threats to American interests and allies, as the Trump administration draws down US troops in Syria and shifts its focus in the Middle East to a looming confrontation with Iran.

“However weakened Isis may now be, they are still a truly global movement, and we are globally vulnerable,” Suzanne Raine, a former head of Britain’s Joint Terrorism Analysis Centre, said in an interview this month with West Point’s Combating Terrorism Centre. “Nothing should surprise us about what happens next.”

Donald Trump presents map to reporters showing how Isis stronghold has depleted since 2016

For Iraqis in northern and western provinces where the Islamic State was active in the past, the sense of threat never disappeared, as the attacks slowed but never halted.

In just the first six months of this year, there were 139 attacks in those provinces – Ninevah, Salahuddin, Kirkuk, Diyala and Anbar – and 274 people were killed. The majority of the dead were civilians but also included Iraqi security forces and popular mobilisation forces, according to reports by Iraqi security forces and civilians gathered by The New York Times.

Earlier this month, a US Marine Raider, Gunnery Sergeant Scott A Koppenhafer was killed in northern Iraq during an operation with local forces. Marine Raiders, who are Special Operations forces, often fight alongside Kurdish peshmerga, or the Iraqi special operations forces, when deployed to Iraq.

His death marked the first American killed in combat in Iraq this year. In January, four Americans were killed in a suicide bombing in Manbij, Syria.

Reports like these fill several new, sobering assessments of the Islamic State’s resilience and potency. A July report by UN analysts on the Security Council Counter-Terrorism Committee said that Islamic State leaders, despite their military defeat in Syria and Iraq, are “adapting, consolidating and creating conditions for an eventual resurgence” in those countries.

A new inspector general’s report assessing Islamic State activities from April through June concluded the group was “resurging in Syria” and had “solidified its insurgent capabilities in Iraq.”

Despite these reports, Mr Trump has continued to claim credit for completely defeating the Islamic State, contradicting repeated warnings from his own intelligence and counterterrorism officials that Isis remains a lethal force.

“We did a great job,” Mr Trump said last month. “We have 100 per cent of the caliphate, and we’re rapidly pulling out of Syria. We’ll be out of there pretty soon. And let them handle their own problems. Syria can handle their own problems – along with Iran, along with Russia, along with Iraq, along with Turkey. We’re 7,000 miles away.”

With 5,200 troops in Iraq and just under 1,000 in Syria, the US military’s role in both countries has changed little despite the territorial defeat of the Islamic State in both countries.

After the fall of Baghouz, the Islamic State’s last holdout in Syria near the Iraqi border, what remained of the group’s fighters dispersed throughout the region, starting what US officials now say will be an enduring insurgency.