Britain must show the same resolve it displayed against Hitler during the Blitz in order to defeat the threat of terrorism, Prime Minister David Cameron has said, as he set out plans for a significant boost in spending on special forces.
Mr Cameron announced plans to spend an additional £2 billion on the SAS and other special units over the coming five years to improve their fighting capabilities.
It is understood that the money will not be used on a recruitment drive, but will fund new weapons and vehicles - possibly including helicopters - protective equipment, night-fighting kit and communications.
In a high-profile speech to the Lord Mayor of London's Banquet, Mr Cameron said the additional cash will be delivered from the growth in defence budgets guaranteed by the Government's commitment to spend 2% of GDP on the military.
The rising military budget would mean "more money every year" for priorities like unmanned drones, fighter aircraft and cyber-defences, he said.
The Prime Minister said the new National Security Strategy he is unveiling next week will give Britain the resources it needs to "increase both its hard and soft power" and boost its influence in the world.
In a swipe apparently aimed at Labour leader Jeremy Corbyn, Mr Cameron said: "Whatever others might wish were the case, the reality is that there are times when you do need to be able to deploy military force.
"And if you don't have it, you can't deploy it."
Mr Cameron also announced he will increase the proportion of the overseas aid budget devoted to stabilising and supporting broken and fragile states from a target of 30% to 50%.
Speaking in London's Guildhall, which was badly damaged by German bombers during the Second World War, the Prime Minister recalled how Churchill had vowed that "however long and hard the toil may be the British nation would never enter into negotiations with Hitler".
And he added: "It is that same resolve that will defeat this terrorism and ensure that the values we believe in - and the values we defend - will again in the end prevail."
Mr Cameron delivered his speech immediately after flying home from a G20 summit in Turkey where leaders of the world's major economies agreed to co-operate in the fight against terrorism in the wake of the slaughter of 129 people in Paris.
Although Russian President Vladimir Putin resisted concerted Western pressure to acquiesce in the removal of his ally Bashar Assad as president of Syria, Mr Cameron detected signs of willingness to compromise on all sides in the search for a solution to the country's long-running civil war.
He pressed Putin to direct airstrikes not at the moderate opposition to Assad's regime, but at the Islamic State terror group which has claimed responsibility for the Paris attacks as well as the downing of a Russian airliner over Egypt.
In signs of deepening political division over defence policy, Mr Corbyn questioned the legality of the drone strike which killed the Islamic State militant nicknamed "Jihadi John", and said he was "not happy" with the idea of a shoot-to-kill policy against terrorists on British streets.
"I would only authorise actions that are legal in the terms of international law," said the Labour leader. "Surely if somebody is doing something wrong you act legally against them."
The Labour leader ruled out a free vote for his MPs on the extension of RAF airstrikes from Iraq into Syria, saying a bombing campaign "may well make the situation far worse".
But Mr Cameron dismissed such ideas in his speech, saying: "Those who say we should have somehow arrested Jihadi John don't get the reality of the world we are in...
"You do not protect people by sitting around and wishing for another world. You have to act in this one. And that means being prepared to use military force where necessary."
He was equally dismissive of critics who questioned his decision to welcome the leaders of countries with dubious human rights records - like China, Egypt and Kazakhstan - to London for official visits.
"You can't conduct foreign policy by press releases and pious statements in Parliament," said the Prime Minister. "You have to engage and build the alliances that can make a difference."
This engagement contributed towards the "soft power" which enabled Britain to "pack a real punch" in influencing the way the world responds to crises, Mr Cameron said.
Focusing more of the Department for International Development's budget on fragile states would "make our aid spending an even more fundamental part of our strategy to keep this country safe (and) help to maintain Britain's position as number one in the world for soft power".
The PM also announced plans to back Muslims who support Britain's values "with practical help, with funding, campaigns, protection and political representation", arguing that the UK "can't stand neutral in this battle of ideas" within Islam.
Dealing with European Muslims radicalised by the "poisonous narrative" of the terror gangs requires a "full spectrum" approach involving military power, counter-terrorism expertise and action to counter extremist ideology, he said.