Millions watch inauguration from home as chief justice administers oath of office at Capitol, two weeks after mob riotJoe Biden sworn in as president – follow live Joe Biden, the new president of the United States, with his wife Dr Jill Biden on Wednesday. At 78, Biden is the oldest president ever to take the oath of office. Photograph: Win McNamee/AP Joseph Robinette Biden Jr has been sworn in as the 46th president of the United States, promising to marshal a spirit of national unity to guide the country through one of the most perilous chapters in American history. Millions of Americans watched from home as Chief Justice John Roberts administered the oath of office to Biden on the steps outside the West Front of the US Capitol, just two weeks after they watched in horror as a mob of supporters loyal to his predecessor stormed the building in a violent last stand to overturn the results of the presidential election. Donald Trump, who never formally conceded his defeat, left the White House on Wednesday morning and was not in attendance, a final display of irreverence for the traditions and norms that have long shaped the presidency. Mike Pence, the outgoing vice-president, was there, joined by the Clintons, the Bushes and the Obamas. Fear and anxiety surrounded the lead-up to Biden’s inauguration. The threat of more violence resulted in the deployment of nearly 25,000 national guard troops, transforming the shining city upon a hill into a military fortress. The pandemic had already greatly reshaped the inaugural events and ceremony, which typically draws hundreds of thousands of spectators to the National Mall. Much of the area was closed. Instead, flags from the states and territories represented those who the inaugural committee had urged to stay away, out of concern that large crowds would spread the coronavirus, which has now killed more than 400,000 Americans. Biden swore to defend the constitution and the country “against all enemies, foreign and domestic”. At 78, he is the oldest president ever to take the oath of office. Part of Biden’s legacy was secured even before he placed his hand atop a large, 19th-century Bible, a family heirloom accented with a Celtic cross and held by his wife, Jill Biden. Biden, the vice-president to the nation’s first black president, elevated Kamala Harris as America’s first female, first Black and first Asian American vice-president. The inauguration brings to a close one of the most volatile transitions in modern memory, an interregnum that tested the fragility of America’s commitment to an orderly and peaceful transition of power. For weeks after his defeat, Trump whipped up loyalists with baseless allegations of a stolen election. His claims were dismissed by dozens of courts, security experts, Republican election officials and his then-attorney general. But Trump refused to accept his fate, a decision that culminated two weeks ago in the assault on the US Capitol, where rioters attempted to stop Congress from certifying Biden’s win. Hours after being sworn in, Biden was expected to return to the White House to begin undoing what his chief of staff described as “the gravest damages” of his predecessor’s legacy. With a sense of urgency intended to reflect the magnitude of the tasks before him, Biden will sign 15 executive orders, as well as a flurry of memorandums and decrees from the Oval Office, according to his top policy advisers. Joe Biden with Jill Biden, and Kamala Harris with her husband Doug Emhoff, at the Capitol. Senators Roy Blunt and Amy Klobuchar are also in attendance. Photograph: Mike Segar/Reuters He will immediately rejoin the Paris climate accords, end the effort to leave the World Health Organization, repeal a travel ban on several predominantly Muslim countries, revoke the permit for the Keystone XL pipeline and extend a pause on student loan payments and a federal moratorium on evictions and foreclosures. He will also send a sweeping immigration bill to Congress and impose a national mandate requiring mask wearing in federal buildings and interstate travel. Taken together, the Biden administration hopes to mark a sharp break with the reality show drama that captured the White House for the last four years by demonstrating a commitment to the work of governing. Nearly half a century after he was sworn in as one of the nation’s youngest senators, he became the oldest president to take the oath of office. A veteran of Washington first elected to the Senate in 1972, where he served until becoming vice-president under Barack Obama in 2009, Biden enters the White House with one of the deepest resumés in American political history, experience he will rely on as inherits a country ravaged by disease, economic turmoil and political upheaval. Loss and recovery have marked his long career in public service. His first wife and his daughter were killed in a car accident days after his election to the Senate. In 2015, he buried his eldest son, Beau, who died of brain cancer. In a tearful farewell address to his home state of Delaware on the eve of his inauguration, Biden said: “I only have one regret: that he’s not here.” Biden’s rise to the presidency, the realization of a life’s dream, was paved with false starts and bad timing. A plagiarism scandal plagued his first run. Outshined by the history-making candidacy of his Democratic opponents in 2008, Biden bowed out beforehand the Iowa caucuses. Then, in 2015, still mourning the loss of his son, Biden opted not to run. But Trump’s presidency tormented him. Trump’s failure to forcefully condemn the white supremacist violence in Charlottesville was Biden’s motivation for launching a third presidential bid. Biden presented himself as a rebuke to Trump – an empathetic figure shaped by personal tragedy who believed he had something to offer the country at a moment of cascading national tragedy. A historic number of Americans, exhausted by the chaos and division of the past four years, elected Biden in November. At the conclusion of the ceremony, the new president will conduct a review of military troops, a tradition intended to symbolize the peaceful transfer of power. Forgoing the time-honored parade along Pennsylvania Avenue, the new president, vice-president and their families will be escorted to the White House by representatives from every branch of the military for one city block. Biden’s day began when he left the Blair House for a Catholic mass at the Cathedral of St Matthew the Apostle, where he was joined by the second couple and congressional leaders in a show of bipartisanship and ritual . Biden, a man of deep faith, will be only the second Catholic president, after John Kennedy.