The aircraft-carrier Queen Elizabeth, with two squadrons of F-35 stealth fighters on board, will be sent into disputed waters in the Pacific in a display of “hard power”, the defence secretary is due to announce in a major speech on Britain’s military strategy in the post-Brexit world.

Gavin Williamson will declare the UK “may have to intervene” in future to confront aggression from countries like Russia and China who “flout international law” and are “resurgent” in rebuilding their armed forces.

Britain and its western allies have to be ready “to use hard power to support our interests”, the defence secretary is due to say in an address at RUSI (Royal United Services Institute) in London on Monday. “We have to be ready to show the high price of aggressive behaviour, ready to strengthen our resilience.”

Mr Williamson will say: “Britain has its greatest opportunity in 50 years to redefine its role as we leave the European Union. And with the world changing so rapidly it is up to us to seize the opportunity that Brexit brings.

“We can build new alliances, rekindle old ones and, most importantly, make it clear that we are the country that will act when required, and a nation that people can turn to when the world needs leadership.”

The defence secretary says part of the £1.8bn increase in the defence budget will fund “very significant investment” in offensive cyber operations and defence against hostile attacks on British networks. There will also be a multi-million pound war-fighting fund, with contributions from all three services to develop innovative equipment.

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Mr Williamson’s focus on “hard power” is a shift from the emphasis by successive UK governments on using “soft power” – diplomacy, trade and cultural exchanges – to spread British influence abroad after the long and costly wars in Iraq and Afghanistan.

Sources close to Mr Williamson stress that he is fully behind using “soft power” tools but believes there must also be a willingness to deploy the armed forces when necessary. “History has taught us that crisis comes when it is least expected,” he is expected to say. “As uncertainty grows we must be ready to act and bring others with us.”

In December Mr Williamson visited Odessa, the home port of the Ukrainian ships seized by Russian forces in the Black Sea and announced that he intended to send warships into the region to assert freedom of navigation. Moscow described the visit as an act of “provocation.”

The planned Pacific voyage of Queen Elizabeth with its complement of Joint Strike Fighters (JSFs) will take the carrier into a naval arena of rising tension.

China is in dispute with neighbouring states and America over the ownership of a number of islands in the Pacific and Indian Oceans, its claims on territorial waters and the building of naval bases, the so-called “string of pearls”.

Japan, India, Australia and the US have formed the Quadrilateral Security Dialogue group, with joint naval exercises. Beijing holds the group as a hostile enterprise, aimed at isolating China, and it has described foreign warships asserting freedom of navigation in the South China Seas as a threat to its sovereignty.

Michael Clarke, a senior fellow at RUSI, said: “Leaving aside the wrongs and rights of Brexit, there is a need for Britain to engage with the rest of the world. There is nothing wrong with the Queen Elizabeth being sent to the Pacific in this kind of a deployment, after all we have already got forces back east of Suez.

“Gavin Williamson seems to want to make his mark. He sees defence as an extension of foreign policy. And, so far, he has emerged as one of the very few ministers in this Conservative government whose reputation has not been badly damaged by the Brexit crisis.

“The question, though, is whether he will be able to get the support of the rest of the government, his fellow ministers, in this forward policy.”

General Sir Richard Barrons, who had served in Iraq, Afghanistan and Northern Ireland, commented: “There was a lot of talk of ‘soft power’, especially at the end of the Cold War, but ‘hard power’ is now back in fashion.

“We have seen how certain states have taken belligerent, aggressive approach in international relations. It is the right policy that the UK should take its share of responsibility along with allies in trying to enforce the international rules based order, and the Queen Elizabeth and the JSFs is probably the right way to do it.

“The question now is whether this can be maintained in the long run with the defence budget being thinned out over 30 years.”

Labour’s shadow defence secretary Nia Griffiths said “The UK’s ability to play our role on the international stage has been completely undermined by eight years of Tory defence cuts. The Conservatives have slashed the defence budget by over £9bn in real terms since 2010 and they are cutting armed forces numbers year after year.”