Theresa wrote an article for the Daily Mail explaining how she will make the UK's defence an important priority if she becomes Prime Minister
As Home Secretary, I have been the Cabinet minister responsible for counter-terrorism for the past six years.
Every week, I receive a personal briefing from the Director-General of MI5. I chair a weekly security meeting with representatives of all the country's security and intelligence agencies, military and police.
I am a member of the National Security Council. I am, at times of high alert, called upon to chair meetings of Cobra, the Government's committee for dealing with emergencies. And every day I am given operational intelligence briefings about threats to our national security.
Those threats are serious. The collapse of Syria led to the emergence of Islamic State, the brutal organisation that not only wants to attack Western countries but has ambitions to build a permanent, functioning terrorist state. Its intentions are well-known, but it is far from the only threat we face. There is Boko Haram in Nigeria, Al Qaeda in the Arabian Peninsula in Yemen, similar groups operating in Libya, Al Shabaab in East Africa, and terrorist planning taking place in Pakistan and Afghanistan.
With such a diverse and rapidly changing terrorist threat, I know that some people say we should question some of the received wisdom when it comes to Britain's defence and security. With the danger mainly coming from terrorist organisations, they say, the need for significant, conventional military forces has changed. With other nation states no longer the main concern, they argue, the need for Britain to retain its own nuclear deterrent is no more.
I disagree on both counts. The world has become a more dangerous place than it has been for many years, and a Conservative Government I lead will make a strong defence an important priority.
It is vital for our national interest that we maintain what is the most significant security and military capability in Europe – backed up by our commitment to spend 2 per cent of gross domestic product on defence – and that we are able to project our power around the world. In particular, it is crucial that we maintain our independent nuclear deterrent.
For while it is true that the terrorist threat has grown more serious, it does not mean we no longer face a threat from conventional enemies in the form of other nation states.
And it certainly does not mean there will be no threat from nuclear states in the coming decades.
We have all witnessed the renewed belligerence of Russia in recent years, most notoriously in the case of its illegal annexation of Crimea, and Vladimir Putin is intent upon upgrading Russia's nuclear forces. The Russian military has increased the number of nuclear exercises it conducts, while Putin threatens to base nuclear forces in the Crimea and Kaliningrad, the Russian exclave on the Baltic Sea that neighbours Poland and Lithuania.
North Korea also continues to defy international law with its nuclear programme. It is the only country in the world to have tested nuclear weapons in this century. Pyongyang says it has withdrawn from the Nuclear Non-Proliferation Treaty, and its provocative flaunting of its nuclear capabilities is something that we should continue to worry about.
These are the reasons the Strategic Defence and Security Review – a process in which I, as Home Secretary, played an active role – concluded that there is a 'continuing risk of further proliferation of nuclear weapons' and warned that we cannot 'relax our guard' or 'rule out further shifts which would put us under grave threat'.
In the face of such strong evidence, it would be sheer madness to contemplate even for a moment giving up Britain's independent nuclear deterrent. And there is no room for compromise, and no room for cheese paring.
We need a full fleet of four submarines, capable between them of providing what the military call 'Continuous At Sea Deterrence', or permanent, around-the-clock cover.
Doing so will send an important message that, as Britain leaves the European Union, we remain committed to working alongside our NATO allies and playing our full role in the world. That is what I know the Prime Minister and Michael Fallon, the Defence Secretary, will be telling our allies when they attend the Warsaw summit this week.
A lot of parliamentary business has, for obvious reasons, been put on hold until the leadership election is complete and a new prime minister is in post.
But when it comes to the nuclear deterrent, the national interest is clear, the Conservatives are united, and we have waited long enough.
The House of Commons should, before the summer recess, vote on Britain's next-generation nuclear deterrent – and we should get on with getting it built.
This article was published in the Daily Mail on 5 July 2016.
