Britain is to create two 5,000-strong rapid-reaction "strike brigades" capable of being deployed across the world, David Cameron is to announce on Monday.
A new fleet of maritime patrol aircraft will also be bought to help ensure the armed forces are adequately equipped for the next five years.
The Prime Minister will give details of an additional £12 billion of equipment spending when he sets out the Government's National Security Strategy and Strategic Defence and Security Review (SDSR) in the Commons.
Among the other announcements will be a 10-year extension to the operational lifespan of the RAF's Typhoon jets and upgrade work to give them ground attack capabilities. They will also be fitted with upgraded stealth radar equipment.
The Typhoons will now be used until 2040, meaning there will be seven squadrons of around 12 aircraft.
George Osborne has revealed that the purchase of F35 Joint Strike Fighter jets for the Royal Navy's two new aircraft carriers will be accelerated - making 24 available by 2023 rather than the previously planned eight.
It has already been announced that the SAS and other special forces will get an extra £2 billion to improve their equipment, the RAF will double its number of drones, an extra £1.9 billion will be spent on cyber security and 1,900 new spies recruited.
Mr Cameron, who will return to parliament later in the week to make the case for air strikes against so-called Islamic State in Syria, said the strategy was based around "an understanding that we cannot choose between conventional defences against state-based threats and the need to counter threats that do not recognise national borders".
"Today we face both and we must respond to both," he wrote in the foreword to the SDSR.
"So, over the course of this Parliament, our priorities are to deter state-based threats, tackle terrorism, remain a world leader in cyber security and ensure we have the capability to respond rapidly to crises as they emerge.
"From the rise of Isil and greater instability in the Middle East, to the crisis in Ukraine, the threat of cyber attacks and the risk of pandemics, the world is more dangerous and uncertain today than five years ago."
Unions believe the spending will result in cuts to the Ministry of Defence's civilian workforce.