The Cuban Missile Crisis of October 1962 had struck real terror in the hearts of Americans (and others around the world) as the superpowers came as close as they’d ever come to waging all-out nuclear war. With Soviet nuclear missiles stationed just 90 miles from the coast of Florida, the Cold war was heating up and the unthinkable looked like it was actually about to happen at any second. The crisis was over by the end of the month, but they were a terrifying few weeks – it was later revealed that a Soviet submarine, surrounded by US Navy vessels, came within minutes of using a nuclear torpedo, convinced that war had started – and the crisis was a major psychological shock to the system in the States and abroad.

Two years later, a pair of nuclear war films were released that plugged into the still palpable paranoia surrounding the events of October 1962. One was Stanley Kubrick’s blacker than black comedy Dr Strangelove or: How I Learned to Stop Worrying and Love the Bomb, which opened in the States in January that year. The other was Sidney Lumet’s Fail Safe, which followed in October. Where Kubrick had poked fun at the most traumatising of subjects, Lumet treated the threat of nuclear war with the deadly seriousness it deserved. Kubrick worried that Fail Safe might damage his film’s box office and he and his producers took Lumet to court (despite the fact that both men were working for Columbia Pictures), resulting in an agreement that Strangelove open in cinemas first.

There are some points of similarity between the two films, so much so in fact that Peter George, author of the novel Red Alert that Kubrick was using as the basis for his film, had already sued Eugene Burdick and Harvey Wheeler for plagiarism over their book Fail-Safe that formed the basis of Lumet’s film. But importantly, it was the tone that set the two films apart. United States Air Force General Black (Dan O’Herlihy) is suffering a recurring nightmare in which a Spanish matador kills a bull. In Washington, D.C., he attends a conference led by Dr Groeteschele (Walter Matthau), a political scientist specialising in the politics of nuclear weapons and a Hawkish, virulently anti-Communist advisor to the never-named President of the United States (Henry Fonda). During the conference, American radars detect an unidentified aircraft wandering into US airspace. Although it’s eventually identified as an off-course civilian airliner, various bomber groups have been despatched to their “fail safe” positions, the point at which an attack cannot be called off. Although most of the bombers are successful stood down, a computer error means that Bomber Group 6 accidentally receives what appear to be valid orders for a nuclear attack on Moscow. All attempts to rescind the order fail, partly because of a Soviet countermeasures system that interferes with USAF radio communications.

As Group 6’s Colonel Jack Grady (Edward Binns) and his crew close in on Moscow, the President agrees to despatch fighters to shoot down the bombers before they can reach their target, while Groeteschele insists that the Soviets will capitulate in the face of the threat of imminent destruction and surrender. The fighters are unable to intercept the bombers and General Bogan (Frank Overton) begins to advise the Soviets on how to trigger the aircraft’s defence missiles. Most of the bomber group are destroyed, but Grady’s aircraft gets through. To appease the Russians and deter potential nuclear holocaust, the President makes a fateful decision – if Moscow is destroyed, he will arrange for New York City, where his wife is currently visiting, to be nuked by a USAF bomber piloted by Black…

Despite featuring two actors better known for their comedic roles (Matthau, chillingly arrogant, and Larry Hagman as the President’s translator), Fail Safe is relentlessly bleak and despairing. It’s brilliant, but there are no laughs to be had here. While Strangelove is a riot from beginning to end, Fail Safe is dour and serious which may explain why it didn’t perform as well as Kubrick’s film at the box office – after the horrors of the Cuban Missile Crisis, the public were in the mood to laugh in the face of nuclear destruction it seems, not to be reminded of the awful reality of the situation. It’s led to the film’s entirely undeserved reputation as being simply the “serious” version of Dr Strangelove when in fact it’s a tense, intelligent and superbly crafted film in its own right.

The ending has often been decried as a little absurd – would a US President really order the destruction of his county’s most populace city to placate the Russians? But then what choice does he have? The Russians would almost certainly have reacted to the destruction of Moscow by letting loose their entire nuclear arsenal and indeed there’s no guarantee at the end of the film that they won’t just do that very thing. The film ends in a powerful montage of crash zooms into still images of life in New York going on as normal, its inhabitants entirely unaware of what’s about to happen.

The ending – which is genuinely is genuinely chilling rather than absurd – is sold largely thanks to the superb performance of Fonda as the quintessential screen US President under pressure. His utter conviction throughout is compelling and he’s joined by an outstanding cast of some of the best acting talent of the day. Matthau is as far from his comic roles as possible as the cold and fanatical Groeteschele and is as mesmerising as Fonda; Hagman is terrific as the out-of-his-depth translator caught up in events he was never trained to deal with; and O’Herlihy, Overton, Fritz Weaver and Binns make more of potentially stereotypical military roles than one might have expected (Dom DeLuise, another actor best known for his comedy, turns up too as a traumatised master sergeant).

Coupled with Lumet’s claustrophobic direction (all sweaty close-ups of increasingly frazzled men – there are very few women in Fail Safe – in moodily lit underground bunkers), it results in a first-rate film that deserves to be a lot more respected than as a simple Strangelove wannabe. Lumet heightens the documentary feel by doing away with a score (the use of silence is exceptional) and uses the performances and the unfolding situation to masterly ramp up the tension. The film starts with an intimate moment, one man’s nightmare, and slowly, with horrible inevitability, becomes everyone’s nightmare. The ending still packs a considerable punch even all these decades later – the only things comparable in 60s films are perhaps the similarly despairing climax of James B. Harris’ tale of nuclear cat-and-mouse, The Bedford Incident released the following year and the post-nuclear jolt of the final image in Franklin J. Schaffner’s Planet of the Apes (1968).

Fail Safe is a slow and thoughtful film, packed with debates on whether or not nuclear wars could actually be won (astonishing as it seems, in the 60s survivability was still a widespread belief in some circles) and it’s all as chilling as you might expect. But as the film goes along and the characters come to realise that our over-reliance on technology has finally come around to bite us, it becomes increasingly unsettling. It should be dull, but it never is, thanks equally to the performances, Lumet’s direction, Walter Bernstein’s screenplay and Ralph Rosenblum’s terrific editing.

Fail Safe doesn’t always get as much love as some of Lumet’s other films (though it does sit in an extraordinary filmography that includes classics like 12 Angry Men (1957), Long Day’s Journey into Night (1962), The Hill (1965), The Offence (1973), Network (1976) and so many others), but it really should. It’s one of his very best, beautifully shot by Gerald Hirschfield, directed for maximum suspense and brilliantly acted. It’s an outstanding film, every bit the equal of Dr Strangelove. Indeed, in some respects, it might even be the better film.