The Labour leader is opposed to Trident, wants talks with Argentina over the Falklands and voted against intervention in Syria. His stance has put him on a collision course with military chiefs, who have always been wary of political meddling

The Army Rumour Service, which calls itself “the British Army’s busiest and best online community”, or Arrse for short, is not somewhere for civilians of a delicate disposition. On the discussion threads of this unofficial website for anonymous serving and former soldiers, anti-capitalist protesters, for example, are described as “hypocritical, unemployable, leeching and parasitic”. “This scum needs a good dose … kicked into them,” concludes a typical post from November. “There is no happiness without order.”

Politicians are written about with contempt, especially leftwing ones – and none more so than Jeremy Corbyn, the least militaristic person since the 30s to command a major British party. He is “an anti-British, not very educated, ageing communist agitating class war zealot”, “an idiot … wannabe radical”.

Since becoming Labour leader five months ago, Corbyn has made clearer and clearer his determination to get rid of Britain’s nuclear weapons. First, he said he would never launch them as prime minister. Then he reshuffled his shadow cabinet and ordered a policy review to undermine Labour’s previous support for them. Then, nine days ago, he suggested – in either a cunning or reckless bid to win the support of leftwing unions with members in the defence industry – that a Corbyn government might deploy Trident submarines without their missiles.

Corbyn has also stubbornly opposed the bombing of Syria, against the view of many of his own MPs; expressed doubts about responding to terrorist attacks with lethal force; and called for Britain to reach “a reasonable accommodation” – reportedly a “power-sharing” agreement – with Argentina over the Falkland Islands, which the British military bloodily recaptured 34 years ago. As one poster on the Army Rumour Service recently put it, Corbyn is “a minor irritant” who has grown into “an unmitigated disaster”.

Facebook Twitter Pinterest The least militaristic person to lead a major British party since the 1930s ... Jeremy Corbyn. Photograph: Tolga Akmen/LNP/Rex/Shutterstock

Exasperation about civilian overseers, or potential overseers, has always been part of British military culture, as I learned growing up in an army family. In a country that fights a lot of wars, the profound gulf between service life and civilian life makes it inevitable. But reactions to Corbyn have gone much further than private barrack-room grumbling.

Last September, only a week after Corbyn’s overwhelming election as leader, the Sunday Times quoted “a senior serving general”, who warned that “feelings are running very high within the armed forces” about the possibility of a Corbyn government. “You can’t put a maverick in charge of a country’s security,” the officer went on. “You would see … generals directly and publicly challenging Corbyn over … Trident, pulling out of Nato and any plans to emasculate and shrink the size of the armed forces … There would be mass resignations at all levels … which would effectively be a mutiny.” If Corbyn proved as militarily radical a premier as promised, “the army just wouldn’t stand for it. The general staff would not allow a prime minister to jeopardise the security of this country and I think people would use whatever means possible, fair or foul, to prevent that.”

On the Arrse website, contributors were typically blunt about what they thought the general meant. “This senior officer is talking about a coup,” wrote one. “Whats[sic] wrong with a Coup if the Generals are loyal to the Crown?” asked another. “Let her decide who runs the country?”

For anyone alarmed by all this, the official military response was not completely reassuring. The Ministry of Defence (MoD) merely described the general’s remarks as “not helpful”. The MoD “ruled out a leak inquiry”, the Independent reported, “on the grounds that it would be impossible to identify the culprit” – even though the Sunday Times had described the officer as “having served in Northern Ireland in the 1980s and 1990s”.

Facebook Twitter Pinterest A shot across the bows ... General Sir Nicholas Houghton on The Andrew Marr Show. Photograph: Jeff Overs/BBC/PA Wire

A few weeks later, on Remembrance Sunday, already one the most charged days of the British national calendar, the head of the armed forces, General Sir Nicholas Houghton, gave a rare interview on the Andrew Marr Show on BBC1. Houghton has a reputation as a thoughtful soldier who says exactly what he means. When Marr asked him for his views on Corbyn’s assertion that he would never use nuclear weapons as prime minister, Houghton replied, “It would worry me if that thought was translated into power.” “So if he wins [the next election], he’s a problem?” asked Marr. Houghton briefly changed the subject. Then he said: “[Nuclear] deterrence rests on the credibility of its use … Most of the politicians I know understand that.”

Despite the coded language, the exchange sounded distinctly like Britain’s most senior serviceman telling Britain’s most senior leftwing politician that one of his core beliefs was unacceptable. “It was a shot across the bows,” says Paul Rogers, professor of peace studies at Bradford university, who has been both studying and teaching the British military for decades. Michael Clarke, director of the Royal United Services Institute, the leading British military thinktank, agrees that Houghton’s implied rebuke of Corbyn was probably no accident: “I imagine he had an inkling it would cause a stir.”

According to most believers in British democracy, political interventions by our military simply do not happen. Ever since the trauma of the English civil war three and a half centuries ago, the argument goes, Britain’s armed forces have always been subservient to civilian leaders – unlike in other countries, rich and poor, western and non-western, with their periodic palace coups and tanks on the streets and generals reinventing themselves as presidents, from Dwight D Eisenhower to Charles de Gaulle.

But as Corbyn’s frictions with the military have revealed, the subservience of our armed forces has limits. Everyone enlisting in the army and RAF swears an oath that they “will be faithful and bear true allegiance to Her Majesty Queen Elizabeth II, Her Heirs and Successors”, and that they will “defend Her Majesty ... against all enemies”. The loyalty to the monarch of the Royal Navy, which was established by royal prerogative, is assumed, so recruits are not required to swear allegiance.

Facebook Twitter Pinterest Inspecting the troops ... everyone who joins the army or RAF swears allegiance to the Queen, not the government of the day. Photograph: Rainer Jens/EPA

“The armed forces don’t belong to the government, they belong to the monarch,” says Clarke. “And they take this very seriously. When [the Conservative] Liam Fox was defence secretary a few years ago, for his first couple of weeks he referred to ‘my forces’ rather than Her Majesty’s forces – as a joke, I think. It really ruffled the military behind the scenes. I heard it from senior people in the army. They told me, ‘We don’t work for him. We work for the Queen.’” If Corbyn makes it into office, his republicanism may challenge this mindset rather more fundamentally.

With the military’s overriding loyalty to the monarchy comes a loyalty to other longstanding British arrangements. “The military are very clear that they have to represent continuity,” says Clarke. “They have a responsibility to the sovereign state.” Between 1912 and 1914, the iconoclastic Liberal government of Herbert Asquith attempted to reshape that sovereign state by granting partial independence to a united Ireland. Ulster Unionists formed an armed militia to resist the policy. When the Asquith government readied British troops to stifle the revolt, their officers threatened to resign en masse. The government backed down, and its Irish independence policy was never enacted.

Half a century later, in 1965, another colony with close links to the British military, Rhodesia, unilaterally declared independence as a way of preserving the dominance of its white settler minority, many of whom were former servicemen. There seemed a chance that the British government, under the Labour prime minister Harold Wilson, would send troops to Rhodesia to impose a less racist political system. Again, there were “mutinous mutterings among senior army officers”, the well-informed defence secretary Denis Healey later recalled. Wilson opted for ineffectual sanctions against Rhodesia instead.

Facebook Twitter Pinterest Harold Wilson ... there were recurring rumours about servicemen plotting to undermine him. Photograph: Roger Jacks/Getty Images

Wilson was a much more mainstream, less disruptive Labour leader than Corbyn; yet throughout his time in office there were recurring Whitehall rumours and press stories about groups of servicemen and ex-servicemen seeking to undermine him. The late 60s and early 70s were a feverish political time, and some of the conspiracies were more real than others. “Sometimes people in the military, at the lower levels, talk as if they want to be a pressure group,” says Clarke. “In the 70s you had a little bit of that. But it was so much froth. The water at the top of the pond” – the high command – “didn’t even shiver.”

Others are less sanguine about what went on. The former Labour minister Chris Mullin was then a leftwing investigative journalist and activist. He watched with alarm the schemes of retired officers such as General Sir Walter Walker, who during 1974 and 1975 became the increasingly dictatorial public face of a new paramilitary volunteer organisation called Unison (later Civil Assistance), which promised to rescue Britain from the “cancer” of the left and the “traitors” in “the militant trade unions”. “Perhaps the country might choose rule by the gun in preference to anarchy,” Walker told the London Evening News in July 1974.

At the time and since, says Mullin, “The [conventional] reaction to Sir Walter Walker was just to dismiss him as a nutter. But he had recently been the commander of Nato in northern Europe.” In the summer of 1974 the Wilson government was sufficiently worried for its new defence secretary, Roy Mason, to warn of a “near fascist groundswell”.

‘Perhaps the country might choose rule by the gun in preference to anarchy’ ... General Sir Walter Walker, c 1955. Photograph: Keystone/Hulton Archive/Getty Images

During the late 70s Walker’s “private army”, as the press called it, disintegrated – not least because Margaret Thatcher’s election as Conservative leader in 1975 gradually convinced many of the general’s supporters that the unions and the left could be crushed instead by an elected government. Yet Britain’s largely forgotten period of military discontent did not end. Between 1975 and 1978 Brian Crozier, a prominent rightwing journalist and activist with views similar to Walker’s, “was invited several times, by different army establishments, to lecture on current [political] problems”. In Harrogate in north Yorkshire, he wrote in his autobiography, he addressed 200 serving officers about “subversive” leftwing politics: the anti-nuclear, anti-military mindset of an increasing number of Labour figures, including Mullin, Corbyn and Tony Benn. “I went so far as to suggest that the army would have to take over,” Crozier (now dead) told me in 2000. “There was this sort of storm of clapping.”

By 1980, with the first Thatcher government struggling, and the Bennites seeming poised to capture the Labour party, the election of a Labour government much more provocative to the military than Wilson’s was becoming a real possibility. On the train back from that year’s party conference, Mullin and other delegates got talking about how the armed forces and the rest of the British establishment would react to such a government. Two years later, Mullin published a thriller speculating on the outcome, A Very British Coup.

Since Corbyn became leader, it has been reprinted twice. Mullin is no John le Carré, but his portrait of a conspiracy by military officers, rightwing newspapers and conservative Whitehall insiders, set in motion after the shock election of a leftwing premier who wants to get rid of Britain’s nuclear weapons, has both been praised for its plausibility and – like anyone who suggests our military might not be democrats in all circumstances – derided as paranoid. Channel 4 broadcast a cult television version in 1988 and another, looser adaptation, Secret State, in 2012. Corbyn knows the book well.

Tellingly, both the novel and the original TV series envisaged a near-bloodless coup. “There had been no tanks on the streets,” says one of the book’s successful plotters with satisfaction. “No one had gone to the firing squad.” Some political acts by our armed forces are seemingly too disturbing for even their fiercest critics to imagine.

Facebook Twitter Pinterest Ray McAnally (right) as leftwing PM Harry Perkins in A Very British Coup. Photograph: BFI

Clarke insists Corbyn has nothing to worry about. “I’ve been hanging around the bazaars of Whitehall for 25 years,” he says, “and if a government decided to abolish nuclear weapons, I believe the military would accept that.” Yet he continues a little less reassuringly: “They [the military] would want to know it was a genuinely democratically mandated decision.” If the government and its anti-nuclear policy had a small majority – and it is hard to imagine Corbyn or such a policy having a large one – the armed forces would, Clarke says, be presented with “a dilemma”. Obstructing the politicians would not have to involve overt threats: “If the government did something the chiefs of staff could not live with, they could resign en masse, which would be pretty disastrous for the government.”

The political neutrality of the military is further weakened by some servicemen’s party loyalties. “Many of the junior ranks vote Labour, but senior officers tend to be Conservative,” says Rogers. According to the BBC, of the 51 current MPs who have served in the armed forces, 49 are Conservatives. Given this, it is hard not to notice the overlap between the Tories’ regular attacks on both Corbyn and his predecessor Ed Miliband as a “threat to national security” and General Houghton’s comments in November about Corbyn.

As in the Wilson and Benn eras, subtle and not-so-subtle messages have been sent by the military to voters, to Labour politicians, to the Labour leader himself, about the risk and even illegitimacy of any leftwing government that pursues radical disarmament. If these messages are absorbed as intended, more dramatic military interventions will never be needed.

Yet less party-political frictions have also built up in recent years between the armed forces and actual British governments, from Tony Blair’s to David Cameron’s. “Relations have not been that happy,” says Clarke. “The campaigns in Iraq and Afghanistan were not as successful as they could have been. The military felt politically unsupported. The politicians felt the military were too optimistic. Retired senior military have spoken out in ways that politicians see as unhelpful: ‘We want more aircraft carriers’ and so on.”

In the era of austerity and Isis, it seems likely that Britain will continue both to fight frequent wars and to inadequately fund its armed forces. It is not a combination to encourage the military to keep out of politics.

During another fraught decade, the 30s, another British administration keen to reduce public spending, the Tory-dominated National Government, imposed pay cuts on the navy. In the isolated but strategic port of Invergordon in Scotland, a large section of the British Atlantic Fleet mutinied. The mutineers even sang the Red Flag. The government was forced to soften the pay cuts. David Cameron take note.