Britain must stop "sleepwalking" and prepare to tackle Muslim extremism as seriously as it planned for the Second World War, a former head of the Armed Forces has warned.
Lord Richards of Herstmonceux said extremism poses a "real threat" to the world and condemned dithering politicians too reluctant to lead the way.
Warning that Islamic State militants would wreak a "hell of a lot of damage" in the coming years, he argued the Armed Forces risk being left "on the back foot" by leaders who fail to plan properly.
"I think the problem is that we have not seen that we need to approach this issue of Muslim extremism as we might approach World War Two back in the 30s," the former Chief of the Defence Staff said. "This is a real threat to us and we're sleepwalking in the way we're approaching it."
He spoke as a new think tank report warns Britain’s military equipment programmes are “in an impossible mess” and the country must increase spending, overhaul the system, or give up hope of pursuing major campaigns in the future.
Politicians are labouring under the “positively dangerous” illusion that the UK is as powerful as it was a decade ago the paper for Civitas warns.
“We either have to spend more, or do things differently, or give up the idea of getting involved in any campaigns that rely on sustained diplomatic effort or military deterrence, let alone on the ability to deliver force,” the report concludes.
Lord Richards criticised politicians including defence secretary Michael Fallon, who "blithely" suggest it will take a "generation" to battle Islamic State of Iraq and the Levant, also known as Isil or Isis.
"We do not have a generation," he said. "In that generation, even in 10 years, a hell of a lot of damage is going to happen and it will continue to draw all sorts of people into their ranks and get stronger and stronger.
"It needs to be dealt with and it is an existential threat to all of us.”
Lord Richards told Chalke Valley History Festival, he would be "most surprised" if Britain did not enter into combat within the next five years, warning Isis must be defeated through "effectively military intervention".
"I'm not necessarily advocating the use of a British armoured brigade and all that implies, but it means a much more comprehensive military strategy that will much more quickly deal with Isis," he said.
"If we aren't in combat again within the next five years I will be most surprised. And as ever it will be forced onto reluctant politicians, and we'll be forced onto the back foot and not as properly prepared for it as we could be if they took the initiative."
Nato leaders on Tuesday said they were poised to return to Iraq in order to fight the Islamic State, four years after leaving the country.
The military alliance is close to launching a mission to train Iraqi officers as the Baghdad government struggles to repel the jihadist group.
The programme, due to be launched next month, will coach senior commanders in developing a national defence strategy and commanding units in the field.
Lord Richards said the British armed forces are "still bl---y good" at the moment, but said the problem was "a lack of political resolve”.
"Our armed forces, properly used and decisively employed, can have a real effect.
"But that isn't the appearance we're creating in the world at the moment.
"Right now, in the ranks of the armed forces, and the army in particular, are the most experienced, battle-hardened people since the end of the Second World War.
"The people are as good as ever they have been and as capable. I actually think that, while we may have too little of it, our equipment is still pretty good.
"I think what really is the issue is our apparent equivocation as a nation.
"What an impact it would have had if Britain was at the forefront of whatever international effort was being created to deal with Isis.
"We're not: we're sort of reluctant, at the back of the queue."
Lord Richards, patron of the Armed Forces Muslim Association, emphasised that he did not believe there was anything in the religion of Islam to encourage extremism, but that "0.1 per cent" of followers had been drawn to a cause and organisations they consider "successful".
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