Britain has pledged to end the "era of retreat" by announcing the biggest military investment sincethe end of the Cold War, despite the coronavirus crisis hitting the economy, as it seeks to define its post-Brexit role on the world stage.
Prime Minister Boris Johnson wants to carve out a leading role for Britain in a new era of global cooperation and free trade, backed by modern military and cyber capabilities.
Mr Johnson said the increased spending reflected the need to upgrade military capabilities, including pioneering new technology with plans for a new space command and artificial intelligence agency.
In a speech to parliament outlining the first conclusions from the biggest review of foreign policy and defence in three decades, Mr Johnson announce an extra £16.5 billion for the military over the next four years.
The defence budget is currently just under £42bn a year.
"I have taken this decision in the teeth of the pandemic because the defence of the realm must come first," Mr Johnson said in a statement.
"The international situation is more perilous and more intensely competitive than at any time since the Cold War and Britain must be true to our history and stand alongside our allies. To achieve this, we need to upgrade our capabilities across the board."
At a time of heightened global uncertainty, the continued rise of China and after four years of US President Donald Trump's international diplomacy, Britain's 2016 vote to leave the European Union has thrown its own role and global influence into doubt.
The new financial deal comes just a week after Mr Johnson promised US President-elect Joe Biden that Britain was determined to remain a valuable military ally.
The government said the increased military spending will cement the UK's position as the largest defence spender in Europe, the second largest in NATO, and allow increased investment in areas such as cyber and space.
Defence minister Ben Wallace said Britain was not growing its military budget at the expense of international aid, amid media reports that billions of pounds could be cut from the foreign aid budget
"It doesn't mean to say we are abandoning the battlefield of international aid, we're still one of the most generous givers of international aid," Mr Wallace told Sky News.
The full conclusions of the defence and security review - a study of threats and capabilities - will be announced next year.