Friday evening brought news of the completion and submission of a long-awaited report by special counsel Robert Mueller, about alleged collusion between aides to Donald Trump and Russian operatives.

Mueller submitted the report to the attorney general, William Barr, who said in a letter to members of Congress he may be in position to advise them of its “principal conclusions’ as soon as this weekend. Calls for the release of the full report followed immediately.

The president, who was at Mar-a-Lago in Florida, did not immediately respond. But in close to two years since the former FBI director started work, he has repeatedly attacked his credibility. In doing so, he has not merely been trying to knock down an investigation Mueller built with stunning speed since he was appointed special counsel in May 2017. He has been attacking his very reputation.

The formidable edifice of Mueller’s personal reputation built over a 50-year career as a public servant, which began with voluntary conscription in the US marines at the age of 21, featured multiple distinguished turns as a federal prosecutor and culminated with the top job at the Federal Bureau of Investigation.

Along the way, Mueller, 74, won a reputation among Republicans and Democrats alike as a hard-working, methodical and serious straight-shooter for whom personal integrity and adherence to the justice department playbook have always been granite-etched fact.

“He is probably America’s straightest arrow, very by-the-book, very professional,” Garrett M Graff, whose book The Threat Matrix studied how Mueller transformed the FBI after the 9/11 attacks, previously told the Guardian.

“He is so straight, he always wears a white shirt,” Thomas B Wilner, a longtime friend, told the Washington Post last year. “He’s a pain in the ass in many ways because he is so straight … He’s conscious that he’s a public figure, and he doesn’t want anything to compromise his integrity. Even a blue shirt.”

Mueller’s seriousness of purpose has been on display throughout his investigation, which within six months had won a guilty plea from former national security adviser Michael Flynn, for lying to investigators.

As Trump has tweeted and raged, repeatedly calling Mueller’s work a witch-hunt, Mueller has remained silent, allowing his work to do the talking. Mueller has indicted or secured guilty pleas from 34 individuals and three companies, including six former Trump aides, five of whom pleaded guilty: Roger Stone has pleaded not guilty, while Flynn, George Papadopoulos, Rick Gates, Paul Manafort and Michael Cohen pleaded guilty). The special counsel is estimated to have clawed back at least $48m through tax fraud cases.

Child of privilege, called to serve

Despite their radically different personal paths, Mueller and Trump, 72, are contemporaries born in New York City to wealth and privilege. Trump, who reportedly had inherited $1m of his father’s real-estate fortune by the age of eight, was packaged off to military school and graduated with an economics degree from the Wharton School in Pennsylvania. Mueller, the son of a navy officer turned chemicals executive, was sent to the exclusive St Paul’s boarding school in New Hampshire and graduated from Princeton.

After the school years, the two men’s lives diverged sharply. While Trump escaped military service via a diagnosis of bone spurs made by a physician who rented his office from Trump’s father, Mueller signed up for the Vietnam war at the bloody height of the conflict. He was shot through the thigh and would be recognized with a Bronze Star for valor in combat, a Purple Heart and other decorations.

“Second Lieutenant Mueller’s courage, aggressive initiative and unwavering devotion to duty at great personal risk were instrumental in the defeat of the enemy force,” the commendation for his Bronze Star read.

Upon his return to the US, Mueller earned a law degree from the University of Virginia and began his career as a federal prosecutor, spending six years in the US attorney’s office in San Francisco and six in the equivalent office in Boston.

After the election of George HW Bush in 1988, Mueller, a lifelong Republican, moved to the justice department in Washington, in short order taking charge of the criminal division, where he oversaw prosecutions of the Panamanian leader Manuel Noriega, the Pan Am flight 103 bombing suspects and organized crime cases.

After a stint in private practice, Mueller signed up to prosecute homicides in 1995 in Washington DC, and was credited with turning the department around. His subsequent work as US attorney in California’s northern district won similar praise, and in July 2001, George W Bush nominated him as FBI director.

The 9/11 attacks fell one week after Mueller was sworn in.

“Bob’s a good marine,” his deputy, Tom Pickard, told Graff for a 2008 profile. “He was very cool under fire.”

“Mueller was at the office around 5am and would work until 11 or midnight,” wrote Graff. “Every day he showed up pressed, clean, and ready for more.”

Mueller’s challenge in the ensuing years was to implement a technological and organizational revolution in the bureau, and to manage a shift in its traditional role from a focus on prosecuting crimes to preventing terrorist attacks.

Mueller’s adherence to the law brought him into conflict with the Bush administration as it built new counter-terrorism tools. In 2004, Mueller and his justice department superior at the time, deputy attorney general James Comey, came within hours of resigning over the planned reauthorization of a dragnet domestic wiretapping program, which Mueller and Comey believed to be illegal. The program was not reauthorized.

When Mueller came to the end of his 10-year term as FBI director, his leadership was the object of such bipartisan admiration that the US Senate, at Barack Obama’s request, voted 100-0 to change the law to extend Mueller’s tenure, which lasted until 2013.

Mueller had spent four years in the private sector by May 2017, when Comey, not yet halfway through his own term as FBI director, was fired by Trump, a move that led to Mueller’s appointment as special counsel – a pivotal moment wheretheir paths crossed once again.