Washington: Under leaden Washington skies on Friday, Donald Trump was sworn-in as the 45th president of the US, an incredible personal achievement for a man with no public service experience who broke all conventions and seemingly took great delight in thumbing his nose at every political and cultural taboo.
In an inauguration speech that read more as a declaration of war than an appeal for the country to unite behind him, Trump signalled a dramatic and unpredictable shift in Washington and the world.
More World News Videos
Trump inauguration speech highlights
Highlights of Donald Trump's first speech as the 45th President of the United States of America.
Before a crowd the size of which will irk him – it was perhaps only half that which greeted his predecessor in 2009 – Trump spoke darkly of today's USA, almost as a failed state in which he promised to turn the lights back on.
"This American carnage stops right here and it stops right now," he claimed in a 16- minute speech which observers deemed unique for its departure from traditional messages that acknowledged the power and strength of American institutions and which invariably stressed unity after polarising election campaigns.
Instead, Trump seemed to tell the country's powerbrokers to hush-up, saying: "The time for empty talk is over … now arrives the hour for action. Do not allow anyone to tell you it cannot be done."
Enthusiastic and scattered protests greeted the new president, and what appeared to be deliberately violent pockets ran amok, with the police reporting more than 200 arrests and a spate of damage to businesses and vehicles. Six officers suffered minor injuries in encounters in which pepper spray, flash grenades and other 'non-lethal' crowd control tools were used.
Within minutes of Trump taking the oath the official White House website was purged, in which nearly all references to climate change were deleted, save for the new president's vow to scrap all Obama's climate policies.
And within hours of taking the oath, Trump took a hatchet to Obamacare, taking time before attending a series of inauguration balls to sign a vaguely and broadly worded executive order in which he ordered federal agencies to change, delay or waive any aspects of the health system that they believed were overly costly for insurers, drug manufacturers, doctors, state governments or patients.
While the website purge was essentially a PR exercise that will require follow-through before the Obama climate initiatives are undone, the strike against Obamacare was seen as a savage blow against the previous president's legacy.
These decisions were intended as signals to Trump's followers that he would hold to his dozens of promised Day 1 actions – though his aids say that the real Day 1 is to be on Monday, when Trump will start working his way through a reported 200 draft executive orders, many of which are described as serving to erase the Obama legacy.
Creating huge expectations as he offered himself as a national saviour, Trump declared: "I will fight for you with every breath in my body, and I will never, ever let you down.
"For too long, a small group in our nation's capital has reaped the rewards of government while the people have born the cost.
"America will start winning again, winning like never before. We will bring back our jobs. We will bring back our borders. We will bring back our wealth. And we will bring back our dreams."
He had a similar sternly worded message for the international community: "We are issuing a new decree to be heard in every city, in every foreign capital, and in every hall of power. From this day forward, a new vision will govern our land - from this moment on, it's going to be America First.
"For many decades, we've enriched foreign industry at the expense of American industry; subsidized the armies of other countries while allowing for the very sad depletion of our military; we've defended other nation's borders while refusing to defend our own; and spent trillions of dollars overseas while America's infrastructure has fallen into disrepair and decay."
He, and Americans, were sick of enriching the world " while the wealth, strength, and confidence of our country has disappeared over the horizon" as factories closed an millions of American workers were abandoned.
"The wealth of our middle class has been ripped from their homes and then redistributed across the entire world. But that is the past. And now we are looking only to the future," Trump said.
In a gesture to a new, unsettling president in an unsettled world, the senate moved quickly on Friday afternoon to confirm the appointment of Trump's defence secretary - Retired Marine Gen. James N. Mattis.
Waved through by a 98-1 senate vote, Mattis, 66, seemed to set his first task as quieting some of Trump's tactless brawling with sections of the services – particularly the intelligence services.
In a statement addressed to US troops, Mattis acknowledged them as "sentinels and guardians of our nation" – but he also credited intelligence personnel and in pledging to work with the State Department to strengthen US alliances abroad, Mattis was seen by some to be rebuking the headstrong new president.