The one word that defined Elizabeth II, CNN.com

"Peter Bergen is CNN's national security analyst, a vice president at New America, an author and a professor of practice at Arizona State University. The views expressed in this commentary are his own. View more opinion on CNN." (CNN) Duty is a rather old-fashioned concept today in a world rife with public figures who hunger only for power to be achieved by any means available. But duty is the one word to best summarize the reign of Queen Elizabeth II, who died on Thursday at 96. The Queen selflessly gave of herself. Hers was a role that is ceremonial, but it is also deeply embedded in the oldest constitutional monarchy in the world and in a country that has given the world so many of the concepts and policies that we associate with democracy. Seven years after the end of World War II, the Queen, aged only 25, ascended to the British throne. Harry Truman was the President of the United States, and Winston Churchill was Prime Minister of the United Kingdom. Since then, the Queen reigned for 13 additional US presidencies: Dwight Eisenhower, John F. Kennedy, Lyndon Johnson, Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Reagan, George H.W. Bush, Bill Clinton, George W. Bush, Barack Obama, Donald Trump and, now, Joe Biden. In many ways the Queen symbolized the "special relationship" between the United Kingdom and the United States. A rite of passage for almost every one of the 14 US presidents since she took the throne was her hosting a state visit for the president in the UK, or her attending a formal state dinner put on by the president in Washington, DC. Most recently she met with President Joe Biden in June at Windsor Castle. According to Robert Hardman, the dean of royal biographers, she was particularly close to Reagan who she found to be "the most charming." They shared a love of the outdoors and of horses. It was a friendship that went on long after Reagan had stepped down as president, Hardman reported in his 2018 book "Queen of the World." The Queen and Obama also enjoyed a close relationship, according to Hardman. She had an extraordinary run; most British subjects can only remember one monarch. During her long reign, the Queen presided over the dissolution of great swaths of the British Empire, continuing a process that began under her father's reign. She also officially installed three women as her prime ministers -- Margaret Thatcher, Theresa May and, just on Tuesday, Liz Truss, who met with the Queen for her formal investiture as prime minister at Balmoral Castle in Scotland. As Queen, she performed an astonishing 21,000 engagements and was patron of hundreds of organizations, including those dedicated to education and training, sports and recreation, faith, arts and culture, according to statistics released by the Royal Household in May when Britain celebrated the Queen's 70 years on the throne. The contrast is striking between who the Queen was and the former British Prime Minister Boris Johnson, who stepped down on Tuesday after being forced out of office. Johnson is a serial liar about matters both large and small, who attended private parties at his official residence at Downing Street during a rigorous Covid-19 lockdown that he himself had authorized. (He later apologized.) The Queen also provided a stark contrast to Trump --whose personal attorney at the time of his 2016 campaign for president, Michael Cohen, paid off a porn actress who claimed to have had an affair with the candidate, and who is recorded to have made more than 30,000 false or misleading statements while he was president, according to the Washington Post. The Queen led an exemplary personal life, and she also rarely spoke in public except at state occasions such as the annual opening of Parliament. Earlier this year she missed her first speech before Parliament for the first time since 1953, and it was delivered in her stead by her son and heir, Charles. It was a telling sign of her increasing frailty. The contents of the Queen's weekly meetings with the 15 British men and women who have served as her prime ministers have mostly remained tightly held secrets, but one can imagine that a monarch who met regularly for seven decades with an extraordinary range of prime ministers from Churchill to Thatcher had some sage advice for many of them. The Queen also was part of a long tradition of strong British female leadership that dates to Queen Boudicia who led a rebellion against the Roman Empire. It was her namesake Elizabeth I who fought off the mighty Spanish Empire, while Queen Victoria ruled during the era that is named after her during which the British Empire became the largest empire in history. It is not an accident, I don't think, that during Elizabeth II's reign the British had three female prime ministers. The British were used to having a female serve as head of state, after all, so having a female leader didn't seem a stretch. Meantime, the United States still has not had one female president. Of course, during her extraordinarily long reign, the Queen made missteps, the most well-known of which was her initial public silence when Princess Diana was killed in a car crash in Paris 25 years ago. The stiff upper lip that had gotten the British thorough the London Blitz during World War II just wasn't the right attitude for a population that was now much more willing to show their emotions publicly. The vast outpouring of public grief that followed Diana's death caught the Queen wrong-footed. She remained in seclusion at Balmoral Castle and only lowered the Union Jack flying over Buckingham Palace after considerable public outrage that the royal family wasn't doing enough publicly to show its grief. But that dissatisfaction has long since dissipated. As she celebrated her Platinum Jubilee on the throne earlier this year, 86% of British citizens said they were satisfied with how the Queen was doing her job. Charles inherits a monarchy that remains broadly popular with the British public. This year 68% of British citizens endorsed the continuation of the monarchy. It is one of Queen Elizabeth II's key legacies and one more example of how she did her duty.