A massive expansion in the number of the UK's anti-terror spies will be unveiled by David Cameron today.
The prime minister will also announce plans to spend millions more helping to improve security at airports in trouble spots around the world.
The moves, to be confirmed in the government's five-year Strategic Defence and Security Review next week, come in the wake of the Paris terrorist attacks and the downing of a Russian jet in Egypt.
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Cameron, who is attending the G20 summit in Turkey, said the moves were needed to protect the "way of life we hold so dear".
He will announce that an additional 1,900 officers, an increase of 15%, are to be recruited for MI5, MI6 and GCHQ.
The prime minister has also ordered a "rapid review" of security at airports in the Middle East and north Africa. Government spending on improving aviation security at home and abroad, including on improving screening technology detecting new threats, is to be more than doubled by 2020.
Cameron said: "Our intelligence agencies work round the clock behind the scenes and as the threat has grown so they too have risen to the challenge. Much of what they do cannot be seen by us or talked about but their courageous and determined efforts allow us to go about our daily life.
"This is a generational struggle that demands we provide more manpower to combat those who would destroy us and our values.
"We will also step up our efforts on aviation security, helping countries around the world to put in place the tightest security measures possible so that we can continue to enjoy places like Egypt and Tunisia and continue with our way of life we hold so dear."
A minute's silence will be held across Europe today to remember the more than 120 people who died in Friday's Paris attacks.