Presidential debate: Donald Trump claims Hillary Clinton has been 'fighting Isis her entire adult life'

The Republican candidate's claim would make Isis 50, or Ms Clinton a young child

Donald Trump claimed Hillary Clinton has been trying to “fight Isis” for 50 years – decades before the group’s existence – in their landmark presidential debate.

Fact-checkers had their work cut out after the two candidates traded blows on Monday night, watched by an estimated 100 million people around the world.

But analysts were astounded when Mr Trump, the candidate for the Republican Party, appeared to claim Isis dated back to the in 1960s.

Donald Trump and Hillary Clinton exchange blows during the Presidential Debate at Hofstra University (Getty)

Ms Clinton had been outlining her policies to tackle the militant group, which controls swathes of Syria, Iraq and Libya and has affiliates launching terror attacks around the world, when her rival interrupted.

“You’re telling the enemy everything you want to do,” Mr Trump said. “No wonder you’ve been fighting Isis your entire adult life.”

The Republican candidate appeared to be stunned by the claim, which triggered a ripple of gasps and laughter in the audience.

“That’s a…that’s…please go to the fact-checkers and get to work,” Ms Clinton said.

Born in 1947, the Democrat candidate is 68 years old and became a legal adult when she turned 18 in 1965.

Isis evolved from a jihadist group established in Iraq by Abu Musab al-Zarqawi in 1999, which was initially known as Jama'at al-Tawhid wal-Jihad, before changing to al-Qaeda in Iraq (AQI) after pledging allegiance to Osama bin Laden’s network in October 2004.

The group waged its insurgency and terror attacks until leaders declared it the Islamic State in Iraq (ISI) in 2006, adding the “and al-Sham [Syria]” to make “Isis” in 2013 after fighters were sent to join the Syrian civil war.

But an internal power struggle between “caliph” Abu Bakr al-Baghdadi and heads of the Syrian arm known as Jabhat al-Nusra caused al-Qaeda to cut ties with Isis in early 2014, shortly before the terrorist group launched its lightning advance across Iraq and Syria.

So depending which date is viewed as the group's foundation, Isis is between two and 12 years old. Mr Trump's gaffe did not go unnoticed among analysts and commentators:

Driving militants out of their strongholds and preventing supporters from launching terror attacks has been a key issue of the presidential campaign.

Mr Trump has previously sparked controversy for proposing “extreme vetting” including a once-floated ban on Muslims entering the US to fight terrorism, and has repeatedly accused Ms Clinton and Barack Obama of fuelling the rise of Isis with “disastrous” policy decisions.

The Republican candidate has repeatedly defended his remarks when challenged, telling CNN: “[President Obama] was the founder. His, the way he got out of Iraq was that that was the founding of Isis, okay?”

Mr Trump’s opponents have accused him of worsening division in the US and fuelling propaganda by Isis and other terror groups that seek to portray a global war on Muslims.

Sadiq Khan, the Mayor of London, said he was “playing into the hands of Isis” during a trip to Canada earlier this month.

“Donald Trump said that Muslims from around the world - I'm paraphrasing - would not be welcome into the United States of America,” he added.

”Not only does that show a lack of understanding and awareness of the great country that is the USA and its history and legacy, it's also inadvertently playing into the hands of Daesh and so-called Isis because it implies it's not possible to be a Western liberal and mainstream Muslim."