Allegations of nefarious plotting, dark charges of betrayal and treachery, and a seeming threat to the very fabric of American democracy.

No, not this summer’s extraordinary congressional probe into the assault on the US Capitol last January, nor the Watergate hearings nearly 50 years ago which brought down Richard Nixon.

Instead, the moment when, two decades before “Tricky Dicky” Nixon's fall from grace, Senator Joe McCarthy’s anti-communist witch hunt reached a dramatic climax as he took on the US Army. A smear, slur and slander too far, it turned the public decisively against him and brought the infamous “Red Scare” of the early Cold War years to a close.

The Army-McCarthy hearings, as they came to be known, feature in US writer and journalist James Kirchick’s fascinating new book Secret City: The Hidden History of Gay Washington. Mr Kirchick, who is Jewish and gay himself, explores how a noxious mix of paranoia and persecution, coupled with secrecy and shame, wrecked the careers, shredded the reputations and ruined the lives of countless gay men and women. And, as the author shows, helped shape the citadel of American power itself.

At the centre of the clash between the US Army and the notorious United States Senate Subcommittee on Investigations was Roy Cohn, the 27-year-old grandson of Russian-Jewish immigrations.

Senator McCarthy’s chief counsel, Mr Cohn is hardly a sympathetic figure. He first caught the attention of the public as the prosecutor who helped send the “atom bomb spies” Ethel and Julius Rosenberg to the electric chair. As Mr Kirchick writes, the fate of his fellow Jews provided with Mr Cohn with “firsthand knowledge of where deviation from American political norms could lead for members of a minority group, a lesson even more pertinent for those who, like him, deviated from sexual ones”. His ruthless pursuit of power – to turn himself from outsider into insider – thus became “a form of personal protection”.

That pursuit – unhindered by sticking to the rules and rooted in the belief that, if you’re not on the attack, you’re playing defence – would later allow Mr Cohn to build a power base in his native New York constructed on his network of contacts. They ranged from FBI director J Edgar Hoover to the Mafia boss Anthony “Fat Tony” Salerno, and included a host of celebrities, judges and City Hall leaders. Among their number was an ambitious young property developer to whom Mr Cohn would later become lawyer, mentor and fixer. As Donald Trump later admiringly suggested: “If you need someone to get vicious toward an opponent, you get Roy.”

But Mr Cohn’s ruthlessness and resilience was first evident in the manner in which he managed to step away from the wreckage of Senator McCarthy’s career – a veritable car crash to which he himself had greatly contributed – largely unscathed.

Over their 36 days, the Army-McCarthy hearings drew huge public attention. Some 80 million Americans – more than half the population – caught at least some of the 187 hours broadcast live by the fledgling television networks.

Their popularity was unsurprising. The drama rested on a battle which both sides were determined to win. Senator McCarthy and Mr Cohn were accused of applying undue pressure on the Army to give preferential treatment to G David Schine, an ex-aide to the former and friend of the later. In return, Senator McCarthy alleged that this was all a smoke-screen: the Army was simply trying to scupper his own investigations into communists within its ranks.

Mr Schine, the wealthy Jewish heir to a hotel chain, appeared to have precious few qualifications for the position of unpaid consultant to which, at Mr Cohn’s insistence, Senator McCarthy appointed him in 1953. And, when Mr Schine was drafted into the US Army in 1953, Mr Cohn began to move heaven and earth – contacting everyone from the Secretary of the Army to his friend’s company commander – to ensure his time in the military wasn’t too arduous. He requested Mr Schine be made an officer; receive extra leave to “work on committee business”; and be assigned to a base close to New York. Mr Cohn roped Senator McCarthy into his campaign, too.

There was, of course, nothing discreet about the Senator and his henchman’s tactics. Mr Cohn threatened to “wreck the Army” and warned the Secretary of the Army he would be “through”. Senator McCarthy, whose committee had already, at Mr Cohn’s urging, launched an investigation into alleged Communist infiltration at the Fort Monmouth military base, accused the Army of using “blackmail” and holding Mr Schine “hostage”.

But what was it about Mr Schine – rich, handsome and possessing, in the words of Time magazine, the “build and features of a junior-grade Greek god” – that led the closeted Mr Cohn to pursue such an obsessive, and potentially dangerous, effort on his behalf?

Many suspected that they knew – and, as Mr Kirchick shows, they weren’t afraid to make it known using the very same tactics of sly insinuation and innuendo that Senator McCarthy and Mr Cohn had themselves deployed so often in the past.

If any moment in the hearings can be said to have led to Senator McCarthy’s fall – within weeks, his approval ratings had cratered, and, by the end of the year, his colleagues had voted to formally censure him for conduct “contrary to senatorial traditions” – it was his confrontation with the Army’s ram-rod chief counsel, Joseph Welch. After the Senator had attacked a young lawyer from Mr Welch’s law firm, he responded: “Until this moment, Senator, I think I never really gauged your cruelty or your recklessness.” As the Wisconsin senator attempted to renew his attack, Mr Welch cut him off with the now-famous and devastating line: “Senator; you've done enough. Have you no sense of decency, sir? At long last, have you left no sense of decency?”

Mr Welch is rightly remembered for delivering this rhetorical riposte which sounded the death-knell of McCarthyism. In that moment, he became, Mr Kirchick writes, “a hero of American liberalism and a national treasure”.

But, as he continues, “less well remembered is Welch’s own trip to the rhetorical gutter at the outset of the hearings”. Questioning a member of Senator McCarthy’s staff, Mr Welch asked repeatedly about the origin of a disputed picture that had been placed in evidence, eventually asking whether it “came from a pixie”. When the Senator foolishly interjected to ask what a pixie was, Mr Welch – wearing “the look of the happy leprechaun” – shot back: “a pixie is a close relative of a fairy”.

“The room erupted in nervous laughter,” suggests Mr Kirchick. “It was the first time during the hearing that anyone had addressed the homosexual undercurrent so central to it.”

Now the rubicon had been crossed, it was open season. Mr Cohn was cross-examined about whether he had ever stayed the night and had breakfast at Mr Schine’s apartment. Joining the chase, Senators asked Mr Cohn whether he had a “special interest” in Mr Schine and questioned his “passionate anxiety” to retain Mr Schine’s services for the committee.

Arrows were fired from all directions. “Representatives from both parties, and from both ends of the ideological spectrum,” notes Mr Kirchick, “felt no moral qualms attacking gay people in furtherance of their political agendas.” For congressmen, the press, and the viewing public, it was simply accepted that gay men and women “deserved to be objects of derision”.

All this, of course, was at a time when the federal government was purging gays and lesbians from its workforce, while the military ferreted out “sexual deviants” within the services. “The lavender scare” – in which Mr Cohn and his boss were ringleaders and participants – underlined that no charge – not even that of being a Communist – was more toxic than that of being, or suspected of being, gay.

Mr Cohn was, as Mr Kirchick argues, both complicit in homophobia and a victim of it. Many years later, for instance, he would oppose New York’s first gay rights legislation by arguing that “homosexual teachers are a grave threat to our children”. In short, as a 2019 documentary about him put it, Mr Cohn was a bully, a coward and a victim.

More broadly, the behaviour of Mr Cohn’s detractors nearly seven decades ago are a reminder that means matter as much as ends. And that those on the left who are so keen to denounce and decry certain historical figures because their attitudes appear archaic from the 21st century may also find some of their own heroes and icons rather flawed when viewed through that harsh lens.