The British military presence in Estonia will be bolstered as Nato dramatically escalates its ability to respond to Vladimir Putin’s Russia.
Leaders from the 30-member alliance are meeting in Madrid for a summit where they will agree to co-operate more closely and significantly increase the number of troops held at high readiness.
The UK already has a significant military presence in Estonia and the Prime Minister will use the summit to expand its headquarters in the Baltic nation.
Officials said this would ensure the UK could provide rapid reinforcements if needed, and deploy artillery, air defence and helicopters.
The alliance plans to have 300,000 troops at high readiness – up from the current 40,000 – and the UK will commit capabilities in land, air and sea to the “new force model”.
Mr Johnson told reporters: “We’ve already got in Estonia a very significant enhanced forward presence of two battlegroups.
“We’re working with premier Kaja Kallas on what we can do to be more supportive to to Estonia, to help them operationally.
“The work is is going on for a close political and military partnership. Our commitment to Estonia, like our commitment to all our Nato friends, is absolute.”
Mr Johnson will also use the Madrid summit to push for greater defence spending across the alliance, despite domestic rows over the UK’s own military funding.
Nato members have a commitment to spend at least 2% of gross domestic product (GDP) – a measure of the size of the economy – on defence, but only nine of the 30-member alliance meet that requirement.
The 2% was always meant to be a floor, not a ceiling, and allies must continue to step up in this time of crisisBoris Johnson
Mr Johnson claims the UK will spend 2.3% this year and will push for allies to do more.
He said: “The Nato alliance keeps our people safe every day. But over the next 10 years the threats around us are only going to grow.
“We need allies – all allies – to dig deep to restore deterrence and ensure defence in the decade ahead.
“The 2% was always meant to be a floor, not a ceiling, and allies must continue to step up in this time of crisis.”
Mr Johnson faces ministers and military chiefs in open revolt about the level of UK spending.
The new head of the Army, General Sir Patrick Sanders, said any further cuts to the size of the British Army – which is set to shrink from a target figure of 82,000 troops to 72,500 – would be “perverse”.
Defence Secretary Ben Wallace said: “For too long defence has lived on a diet of smoke and mirrors, hollowed-out formations and fantasy savings when in the last few years threats from states have started to increase.
“It is now time to signal that the peace dividend is over and investment needs to continue to grow before it becomes too late to address the resurgent threat and the lessons learned in Ukraine. It is time to mobilise, be ready and be relevant.”
Foreign Secretary Liz Truss told MPs: “The free world did not spend enough on defence post the Cold War and we are now paying the consequences.
“I support the aims of increasing defence spending through this Nato summit.”
The Prime Minister appeared to admit he would breach a Tory manifesto commitment for annual above-inflation rises in defence spending, but stressed that the Government was pumping in billions of pounds as part of the biggest defence settlement since the Cold War.
He said “you don’t look at inflation as a single data point”, insisting that over the course of the parliament the manifesto promise would be met.
But with inflation set to hit 11% this year and the public finances battered by the impact of the pandemic, the 2019 election manifesto promise for a real-terms rise every year appeared to have been abandoned.
Mr Johnson defended his approach to the manifesto pledge, saying: “We have been running way ahead of that target for a while now.
“We are confident that we will meet that – you don’t look at inflation as a single data point, you look at it over the life of the parliament and I’m confident we will meet that.”
A senior Government source said: “The manifesto was written before £400 billion had to be spent locking people up for their own safety because of the global pandemic.”
There was a boost for Nato as the summit got under way, with membership for Sweden and Finland moving a step closer.
Turkish President Recep Tayyip Erdogan had blocked the move, insisting the Nordic pair change their stance on Kurdish rebel groups that Turkey considers terrorists.
After urgent top-level talks, Nato secretary general Jens Stoltenberg said: “We now have an agreement that paves the way for Finland and Sweden to join Nato.”
Mr Johnson will meet the leaders of Turkey and the two Nordic nations on the margins of the summit on Wednesday.
The UK had supported the Swedish and Finnish bids to join the alliance.
Mr Johnson said they were “breaking decades of historic neutrality” to join the organisation, which showed the alliance was “in robust health”.
“Sweden and Finland’s membership will make our brilliant alliance stronger and safer,” he said.