War-weariness among the public and wariness among politicians mean next year could be the first since at least 1914 that British soldiers, sailors and air crews are not engaged in fighting

When British forces pull down the union jack for the last time in Afghanistan this year, it will be a hugely symbolic moment. It is not just that the departure marks the end of 13 years of British involvement in combat in that troubled country. The surprise is that it could also signal the end of a century or more of unbroken warfare by British forces.

Next year may be the first since at least 1914 that British soldiers, sailors and air crews will not be engaged in fighting somewhere – the first time Britain is totally at peace with the rest of the world.

Since Britain's declaration of war against Germany in August 1914, not a year has passed without its forces being involved in conflict. It is a statistic that has been largely overlooked, and not one about which the government is likely to boast.

The past 100 years have seen two world wars, large-scale conflicts in Korea and Iraq, and small-scale actions in Africa, the Middle East and Asia. There have been punitive operations in defence of empire, cold war operations, post-9/11 support for the US, and the Troubles in Ireland.

No other country, even those with similarly militaristic traditions, has been engaged continuously over such a long span. Even during 1968, a year often hailed by members of the British armed forces and some military historians as a year of peace, there was fighting.

The timeline of constant combat may stretch even further back, given Britain's imperial engagements, all the way to the creation of the British army in 1707.

Members of the 1st Lancashire Fusiliers on 1 July 1916, during the first world war. Photograph: Hulton Archive/Getty Images

Britain's generals and politicians anticipate that 2015 may be a year finally without conflict and are planning accordingly. Senior military staff describe this as a "strategic pause".

Assuming agreement is reached with the Afghanistan government before the end of the year, a few hundred soldiers will be left behind to help with training at the army academy, and a few others in a consultative role but not for combat. Special forces could be deployed but no one in the Ministry of Defence is going to go public on that.

The potential absence of war is attributed to a number of factors: lack of public support for the Afghanistan and Iraq conflicts; cuts in the size of the army, making it harder to mount similar operations; an increasingly multicultural Britain that could make intervention in Muslim countries more problematic; and antipathy among the present generation of politicians to interventions, as demonstrated by last year's Commons vote against action in Syria.

A report by the International Institute for Strategic Studies this week showed Britain dropping from fourth place to fifth in the world in terms of budget spending on defence. The army is to be cut from 102,000 to 82,500 by 2018.

A second world war bomber aircraft. Photograph: Print Collector/Getty Images

The former Labour defence secretary Lord Browne said: "The British public have made it clear that there is very little support for new expeditionary wars of choice, even where there is a national security dimension. They may tolerate long-range support of oppressed people, but intervention by UK troops is for now off-limits.

"The new generation of British politicians have taken note. They have seen their immediate predecessors' political capital drain away in times of war. In my view, there is a growing reluctance among them to allow the same thing to happen to their generation."

The British position contrasts with that of France, which has been enthusiastically mounting interventions in Africa. There appears not to be the same war-weariness in France, which did not take part in the Iraq invasion.

Colonel Richard Kemp, former commander of British forces in Afghanistan and a participant in many other interventions, from Northern Ireland through to the Balkans and Iraq, said the Syria vote suggested "a higher threshold for British engagement in combat operations in the short term following our experiences in Iraq and Afghanistan".

He said: "The savage cuts inflicted on our forces by this government will severely limit options open for the use of force. In part, they were planned for that purpose – so that in future we could plead inability rather than unwillingness when asked to support our American allies."

An Argentinian bomb explodes on board the Royal Navy frigate HMS Antelope during the Falklands war. Photograph: Martin Cleaver/PA

When senior British military staff refer to a strategic pause, this implies that it is only a matter of time before they see action again. Kemp said: "The world is increasingly dangerous and unstable, especially in the Middle East and parts of Asia. We are still a permanent member of the UN security council with global responsibilities. And no prime minister will be able to resist brandishing military power, however diminished, on the world stage. I therefore predict it will not be long before our forces are again in action somewhere in the world."

A Ministry of Defence thinktank study in November 2012 said the British public had become unsupportive of military action and "casualty-averse", and proposed as alternatives the use of drones, recruiting local proxies to fight on behalf of the UK, and expanding the use of special forces.

A senior British defence official described a year without military action as a problem. Recruiters were already struggling and the prospect of no action in 2015 would not help. "You want to join the army to do stuff," he said.

He anticipated action in the future: "I think after the election the prime minister will have the appetite to get on to the horse again, though we have to make sure it is the right horse. I would be surprised if nothing happens a year and a half or two from now." It could be joint action with the French rather than the Americans, he added.

Senior MoD figures told the Guardian in January that they believed a reluctance among an increasingly multicultural British population to see troops deployed abroad would influence the next two strategic defence reviews.

British troops on patrol in Iraq in 2004. Photograph: Sean Smith for the Guardian

Sir Hew Strachan, one of the UK's leading military historians and professor of the history of war at All Souls College, Oxford, acknowledged that there were constraints on action, ranging from the reduced size of the army through to the increasingly multicultural nature of British society.

Strachan was recently in France, whose forces have been involved in a series of carefully chosen military interventions in Africa, and was struck by the view that Britain had lost its appetite for military action. "It is a reversal of the traditional European military roles," he said.

He attributed some of this to what he called an "unholy alliance" of the chancellor, George Osborne, wanting to save money and the British military wanting to fight but not in badly conceived operations.

Strachan said he could envisage a realignment that would see British forces work more closely with the French military rather than in tandem with the US government as it had over the past decade.

The reduction in the size of the army and a reliance on reservists meant a reduction in state of readiness, he said. In spite of that, David Cameron still aspired to a global reach.

Strachan added the caveat: "There is no guarantee there will not be any action in 2015."

The bodies of seven British soldiers and marines killed in Afghanistan are carried through Wootton Bassett in June 2010. Photograph: Matt Cardy/Getty Images

Tom Petch, a former army officer and director of The Patrol, an award-winning new film about tensions among British soldiers in Afghanistan, identified public opinion and military cutbacks as key factors limiting future action but agreed that multiculturalism would be a factor too.

"Britain is becoming a far more culturally diverse nation, and these interventions have occurred in Muslim nations. In the future, British citizens with Middle Eastern heritage will be less willing to see our forces deployed to their cultural homelands without clear justification."

Professor Richard English, a historian at St Andrews University who studies war and terrorism, said that although many British Muslims had been greatly concerned that their country was waging war in Muslim countries, Britain's war-weariness was a more complex and extensive phenomenon.

"It may be that multiculturalism is a grace note or a second melody in there – I'm not sure that it's the main thing," he said. Instead, he believes war-weariness is focused on Iraq and Afghanistan as a result of what he described as "the dodgy bill of goods" that led to the former and the uncertain achievements of the latter.

"The decision in the House of Commons about Syria was really a decision about Iraq, but a few years late," he said.

English added that war-weariness was a cyclical affair. "It is always easy between conflicts to forget how nasty they are, and this amnesia is one of our worst enemies."

• Explore the interactive timeline, Britain's 100 years of conflict, charting every war in which British forces have been engaged since 1914.