Donald Trump became the 45th president of United States on Friday, and placed the battle against "radical Islamic terrorism" at the heart of his foreign policy, vowing to work with allies to destroy the militant threat.
“We will reinforce old alliances and form new ones and unite the civilised world against radical Islamic terrorism, which we will eradicate completely from the face of the earth,” he declared.
The 70-year-old Republican billionaire placed his left hand on a bible used by Abraham Lincoln and recited the 35-word oath spoken since George Washington, and then launched into a much-anticipated inaugural address.
US President Donald Trump and Vice President Mike Pence stand for the singing of the US National anthem. -Reuters
“We, the citizens of America, are now joined in a great national effort to rebuild our country and restore its promise for all of our people,”
Trump told a crowd of hundreds of thousands massed on the National Mall.
“Together we will determine the course of America, and the world, for many, many years to come,” he said.
“From this day forward, it's going to be only America first.”
Trump's inauguration caps the improbable rise to power of the Manhattan real estate mogul, who had never before held elected office, served in the government or the armed forces.
A crowd of hundreds of thousands looked on, including outgoing president Barack Obama and Trump's defeated election opponent Hillary Clinton - who narrowly missed out on becoming America's first female president.
Meteoric political rise When Trump descended the escalators of his glitzy New York tower in June 2015, his run for office was dismissed and even mocked.
His staff, many shunned by friends for supporting a man who has been labeled a racist and bigot by his critics, will become power players in the White House.
In the primaries, Trump dominated a crowded Republican presidential field with smash-mouth rhetoric and star power. He rode that same wave of anti-elite sentiment to victory over Clinton in the November election.
For Trump's critics, there was disbelief that a man who 19 months ago hosted “The Apprentice” is now leader of the free world.
Time-honoured traditions
At 70 years of age, Trump is the oldest man ever to begin work in the Oval Office.
He has vowed to tear up Obama's policies and re-examine decades-old alliances with Europe and in Asia.Beginning Friday, his team plans a rolling series of daily executive orders to roll back Obama's agenda.
His inauguration was notably more sparsely attended than that of Obama in 2009 and 2013.
Many will look to Trump's inaugural speech for efforts to unify a country divided by politics - and increasingly, by culture.