WASHINGTON — Donald John Trump was inaugurated as the 45th president of the United States on Friday (local time), ushering in a new and more unpredictable era in which he has vowed to shatter the established order and restore American greatness.

From the West Front of the Capitol, overlooking a crowd of admirers gathered as rain threatened on an overcast day, Mr. Trump used his Inaugural Address to promise that he will use the next four years to rebuild the nation’s economy, reassert control over its borders and regain respect for the United States around the world.

“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,” he said.

“Together we will determine the course of America and the world for many, many years to come. We will face challenges. We will confront hardships. But we will get the job done.”

He said the inauguration represented not just the peaceful transfer of power from one part to another. “We are transferring power from Washington, D.C. and giving it back to you the people,” he said.

The newly sworn-in president give the crowd his signature thumbs up. Photo: Getty

“For too long,” he added, “a small group in our nation’s capital has reaped the rewards of government while the people have born the cost.

“Washington flourished but the people did not share in its wealth. Politicians prospered but the jobs left and the factories closed. The establishment protected itself but not the citizens of our country. Their victories have not been your victories. Their triumphs have not been your triumphs.”

He vowed to reverse that trend and make America first. “The forgotten men and women of our country will be forgotten no longer.”

Mr. Trump, wearing a dark suit with red tie and accompanied by Melania Trump in a powder-blue suit, intends to waste little time after taking the 35-word oath that was administered by Chief Justice John G. Roberts Jr. to start unraveling the policies of his departing predecessor, President Obama.

Within hours of taking office, the new president could begin signing executive orders freezing regulations put in place in the last weeks of Mr. Obama’s tenure and reversing policies on health care, immigration and other areas.

His son, Donald Trump Jr., said the new president was coming to grips with the gravity of his new position, even if it did not necessarily seem so in public.

“He’s been humbled by the whole process,” he said on MSNBC. “And you know, whether he shows that outwardly or not is, you know, is one thing.”

President-elect Donald Trump arrives for the presidential inauguration ceremonies on the West front of the U.S. Capitol in Washington

A day of ceremony

Through a long day of pomp and pageantry that will end with three inaugural balls, Mr. Trump will have the opportunity to revel in his moment of triumph.

Surrounded by relatives, lawmakers, former presidents and other dignitaries, including Mr. Obama, and the Democrat he beat last November, Hillary Clinton, Mr. Trump will take command of a country unsettled after one of the most polarising periods in modern times.

His critics have made clear they will not defer even for a day to a new leader they accuse of playing to racism and hatred.

Demonstrators gathered early Friday morning to protest the new president. Liberal groups have organised a march that they expect to draw as many as 200,000 to downtown Washington on Saturday.

People watch in the National Mall during the inauguration.

Violence broke out an hour before Mr. Trump was inaugurated when protesters smashed shop windows around Franklin Square in downtown Washington.

A Bank of America branch had all its windows shattered and a Starbucks was left with a gaping hole in its glass front door.

Police officers in riot helmets used pepper spray to break up groups of protesters, who spread out and kept breaking windows. Bricks and rocks were thrown at police.

Changing direction

For Mr. Trump, the ceremonies capped a remarkable rise to power that defied all expectations, and his ascension amounts to a hostile takeover of a capital facing its most significant disruption in generations. While officially a Republican, Mr. Trump has at times assailed leaders of both parties and positioned himself as the ultimate outsider, making clear that he will follow his own instincts in determining the nation’s course.

America has never seen a president quite like Mr. Trump, the son and grandson of immigrants who grew up to become a real estate magnate, casino owner, beauty pageant operator and reality television star whose tumultuous love life played out on tabloid front pages.

Never before has the presidential oath been administered to someone who had never served either in public office or as a general in the military. At age 70, Mr. Trump will become the oldest president ever sworn in for the first time and the first born in New York since Franklin D. Roosevelt.

He is one of the wealthiest presidents ever to enter the White House, with far-reaching business ties that have already raised questions about where his interests end and the country’s begin.

He arrives in the Oval Office dogged by reports about Russian interference in the election on his behalf and, in the hours before his inauguration, fresh word of a federal investigation into the Russian ties of some of his advisers.

But Mr. Trump overcame the skeptics who did not take him seriously when he embarked on what seemed like a quixotic bid for the presidency. An Ivy League-educated mogul who lives in a tower with an 80-foot-long living room in the heart of the nation’s largest city, he turned himself into the unlikely leader of a populist movement rooted away from the country’s urban and suburban coasts.

The new administration

He takes over on Friday without much of a team in place. Although he has named nominees for every cabinet post, the Senate confirmation process has slowed and few sub-cabinet officials have been announced.

Mr. Trump has asked more than 50 officials from Mr. Obama’s administration, particularly in security agencies, to stay temporarily to ensure the continuity of government.

With the completion of the oath, the Marine Band played “Ruffles and Flourishes” four times and then “Hail to the Chief,” followed by a 21-gun salute.

– The New York Times