The west would like to forget Syria but it refuses to be forgotten. Since the civil war there began in 2011, our expressions of sympathy with its benighted people have followed an oddly cyclical, almost ­ritualistic pattern. Every summer, when our politicians are away on holiday, news from Syria seems to have an odd way of flooding back into the headlines. Something gruesome unfolds that once again draws our attention. There is a tragedy to prick our conscience, or some new horror – perpetrated by the regime or its enemies – to shock our sensibilities.

The crisis in Syria is developing fast. Iranian and Russian involvement is increasing by the week, in addition to the role played by Saudi Arabia and the other Gulf states in funnelling money into the conflict. US policy is likely to develop considerably over the next few months, as it is widely agreed that the existing approach has not achieved its aims. France has announced a new aerial campaign against Islamic State. The real choice facing Britain will be whether it, too, is capable of, or willing to, play a part.

Parliament may be about to begin another hermetically sealed intellectual debate about non-intervention and intervention. But others will continue fiddling in Syria for their own purposes, and Britain will face some of the consequences.

Interfering in the Middle East is a thing of which weary western governments, and their populations, have become extremely wary. It is for understandable reasons that our response to events in the region begins from that premise. What we are now presented with, however, is the corollary: the consequences of a “kick the can down the road” foreign policy.

Some of the results of this seem to resonate with us more than others. Last year it was the fate of the Yazidis threatened by the so-called Islamic State that was the spur to action. The response to the image of the three-year-old boy Aylan Kurdi, dead on a beach in Bodrum, Turkey – one of two Syrian Kurdish children killed in the latest tragedy involving boatloads and convoys of hundreds of thousands of refugees fleeing war zones in the Middle East and North Africa – seems to suggest that reserves of sympathy have not yet been exhausted. Or, at least, that there are still some things that cannot be ignored. Yet the truth is that our compassion is on a sliding scale. We are fast becoming more, not less accustomed to these things.

The refugee crisis has intruded into our neighbourhood, and therefore our collective conscience. But it is just one small example of the further descent of Syria into darkness. That Aylan Kurdi – who died together with his five-year-old brother, Ghalib, and their mother, Rehan – was fleeing the town of Kobane is a reminder of just how connected these things are. Earlier this year, Kobane was given a momentary reprieve after being besieged by Islamic State (IS) for months. US air strikes helped Kurdish fighters take back the town but it remains extremely vulnerable to attacks. The IS capital, Raqqa, is just two and a half hours’ drive away to the south. At the end of June, IS fighters infiltrated the town in disguise, detonated three car bombs and opened fire, massacring more than 100 civilians.

The limitations of air strikes as a method of countering IS, or even of providing ­protection to the civilian population on the ground, are becoming clear. In Syria, Britain’s official position is that it does not take part in air strikes, as it has not had a written request from President Bashar al-Assad to do so – thus, an RAF drone attack on two British civilians in Syrian territory on 21 August has been explained as “self-defence”. In Iraq, where Britain does contribute to the aerial campaign against IS, at the invitation of the Iraqi government, the situation is only marginally better.

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Since Barack Obama’s offensive against Islamic State began nearly a year ago, the self-declared ­caliphate has been deprived of an estimated 10 per cent of the territory that it held at its peak and yet, in fact, IS has increased the range of its attacks – both in Iraq and in Syria. If one considers the activities of its devotees in places such as Tunisia and France, it has spread its wings further still.

IS has weathered the storm and its brazenness is unbounded. At the end of May, just a few hundred IS fighters managed to recapture Ramadi, the capital of Anbar province in Iraq. In August, it was reported to have used mustard gas in Marea, near Aleppo, against other forces also fighting the regime. Having reached Palmyra, its fighters have blown up much of the ancient ruins and executed an 82-year-old guardian of temples from the 1st century AD.

The taking of Palmyra gives IS control of one of the main roads to Damascus, the Syrian capital, which has come under shelling from rebels in recent weeks. Assad – beleaguered but helped by a new infusion of support from allies – has begun a counteroffensive. He is supported principally by Iran. Freed from sanctions on its nuclear programme, Iran has announced a huge increase in military spending and has doubled down its efforts in Syria. In the past few weeks, Russian troops have also been seen on the ground, and more are expected soon. As politicians in Britain talk about the need for a renewed political initiative, no one seems to have noticed that Tehran and Moscow have announced their own “road map” for a Syrian settlement, entirely independent of the west or any serious Sunni partner.

Damascus will not fall without the most horrendous bloodbath. In the middle of August, Assad responded to attacks on the capital by bombing a market in Douma, about ten kilometres north-east, killing roughly a hundred non-combatants. US intelligence officials recently suggested that it is highly likely that he will use chemical weapons again if any of the regime’s strongholds is threatened.

The Syrian conflict and its related ills – including the refugee crisis, the growth of Islamic State, the destabilisation of Iraq, Lebanon and Turkey – contain all the ingredients for further escalation. There is no reason to suggest that we have seen the peak. From IS-inspired attacks to the worst refugee crisis in Europe since the Second World War, it is also clear that these events will continue to impinge on our neighbourhood. A “general consensus” on foreign policy might turn out to be impossible. The Chilcot report hangs like a guillotine over the Labour Party but there is a moment when self-criticism becomes self-indulgent.

With the crises in the Middle East and eastern Ukraine, it has become fashionable once again to talk of a “world order”. Industrial-scale murder, state collapse and huge population displacement on Europe’s borders are symptoms of how old certainties are being undermined.

The very idea of world order has always been subjective. The prevalent world order of the past two centuries has been crafted in an Anglo-American image. It was against this that first the Kaiser, and then Hitler railed in the years leading to the two world wars of the 20th century. It was a countervailing global system that the Soviet Union tried to establish as an alternative during the cold war. Today, the Chinese have a different conception of world order. They want to recraft and rebalance the existing order, though they see merits in maintaining a stable system. Henry Kissinger is among those who have argued that the American and Chinese conceptions of world order are not necessarily incompatible. The two superpowers may reach a new balance and an accommodation; for the moment, however, we may be entering a place somewhere in between. The era of US unipolarity is coming to an end. Yet it is Europe that is feeling the pinch more than the United States.

After the Second World War, the US replaced Britain and France as the dominant external power in the Middle East. It has become tired of that burden. A combination of three things – exhaustion from costly interventions in Afghanistan and Iraq, less dependency on Middle Eastern oil, and a pivot to the east – has made it no longer willing to shoulder this responsibility to the extent that it once did. President Barack Obama believes that the costs now outweigh the benefits, though even he finds that the region repeatedly sucks him back in.

The European nations, Britain included, have not prepared themselves fully for the consequences of this. Even a 10-degree turn of the head in Washington, DC has caused a power vacuum. Their minds and their muscles have atrophied after so many years under the Nato umbrella. Suddenly the ­borders of the region – arbitrary lines drawn in the sand a hundred years ago – look like just that. North Africa, the eastern Mediterranean and the Levant – areas that were once of great strategic importance to Britain – have come back to haunt us, in ways we did not anticipate.

While evoking images of a stable state system – a reassuring equilibrium that satisfies the desire for symmetry and balance – world order also depends on something more intangible: perception. That perception, in turn, implies certain boundaries of conceivable action. A viable world order is therefore one that has some sort of moral foundation. It is not only supposed to prevent large-scale wars between states but also to mitigate catastrophe and to check the worst excesses of human behaviour.

Our moral and mental world order has had its share of shocks to the system since the fall of the Berlin Wall. State failure and mass murder in the Middle East and Africa have precipitated top-level political mobilisation and international activism. The efforts to prevent such things have often been inadequate. And yet, future historians will most likely look back at the turn of the 20th century as bearing witness to a surprising degree of collaboration and co-operation between the world’s leading powers on

issues such as genocide, famine and even climate change.

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Even within this interlude of human history, it was clear that some tragedies were deemed more worthy of action than others. July marked the 20th anniversary of the Srebrenica Massacre. This was a crisis, after all, which unfolded within Europe in the context of western triumph in the cold war. More than anything, the response to Srebrenica is a ­reminder that our moral radar is directed by time and place, by context and locale.

Not every tragedy can be fixed. But history tells us that when the standards by which nations conduct themselves in the international arena begin to slip, the condition can spread quickly. Before long it becomes gangrenous. In 1902 J A Hobson, who had been a reporter in the Boer war – during which Britain was widely condemned for establishing the first mass concentration camps – warned that the behaviour of the leading states was deteriorating rapidly. While Germany and Russia were bolder in their “professed adoption of the material gain of their country as the sole criterion of public conduct”, other nations had “not been slow to accept the standard”. The whole art of diplomacy had been remodelled to make “national aggrandisement without pity or scruple . . . the conscious motive force of foreign policy”. This was a “sliding scale”. Hobson warned that conscious, deliberate adoption of these standards by all the major powers was “a retrograde step fraught with grave perils to the cause of civilisation”.

In 1904, ten years before the First World War, J L Garvin, the influential journalist who went on to take over the editorship of the Observer, agreed with Hobson that the prospect of a general war was increasing every year. The way in which treaties were disrespected and international arbitration was ignored was deeply concerning. But he also argued that it was disastrous to pursue a foreign policy “merely in the spirit of nebulous benevolence towards mankind”. To preserve world order required firm action, rather than nervous hand-wringing. To declare “a plague on both your houses” was not enough. Men such as Hobson had a tendency “to magnify the mote in our own eye, and to accept the assurances of our brother that there is none in his own”. The effort to be impartial became a snare when it led “to special pleading for an enemy or a competitor”. Ominously, Garvin wrote under the pseudonym “Calchas”, the Greek prophet of the Trojan war.

The centenary of the outbreak of the First World War prompted some of our leading historians to compare the crisis that caused it to the one in which we find ourselves today. Chris Clark, the author of The Sleepwalkers: How Europe Went to War in 1914, has warned against making too many comparisons. But the fable of his book – that the statesmen of the era sleepwalked into the crisis, most believing that war was extremely unlikely, and did not see their error until it was too late – is a pertinent one. In international affairs, sometimes things are more fragile than they seem.

Margaret MacMillan, the author of The War That Ended Peace, has been more willing to draw comparisons. She points out that the modern Middle East has certain uncomfortable similarities with the Balkans in the early 20th century – competing ethnic and religious groups, aspirant new nations, revolutionaries and terrorists, and a crumbling of the existing state system. “Instead of muddling along from one crisis to another,” MacMillan recently warned, “now is the time to think again about those dreadful lessons of a century ago in the hope that our leaders, with our encouragement, will think about how they can work together to build a stable international order.”

After 1918 a world order was envisaged but never truly achieved. The Treaty of Versailles did not provide a firm foundation for it, and revisionism began before the ink on it was dry. More importantly, it soon ­became clear that it was easier to challenge the postwar order by force than by discussion. The great tragedy of the interwar years was not the failure to articulate the necessity of a world order, but the failure to stand up for it.

The so-called realists of the interwar era – such as the scholar E H Carr and Neville Chamberlain – put the blame on naive idealists and their fantasies of world government. But this view has been challenged forcibly by Adam Tooze in his most recent book, The Deluge: the Great War and the Remaking of Global Order, 1916-1931. For Tooze, the restless search for a new way of securing order and peace was the expression not of “deluded idealism”, but of a “higher form of realism”.

Its failure can be explained in two ways. First, the fascist and revolutionary powers did everything they could do undermine it and were not answered until it was too late. Second, the United States remained a reluctant Goliath, unsure that it wanted to bear the burden for stability in Europe and the Middle East. For Tooze, even Woodrow Wilson was a somewhat conservative president in this respect, unwilling to pollute the American republic by messy foreign entanglements or sorting out the mess made by others. This is not wildly dissimilar from Obama’s world-view.

For the statesmen of the 1930s, too, the sense in which a carefully constructed order was unravelling fast was tangible and profound. When you read the foreign policy debates from that era, it is hard to ignore the similarities to today: a vague confidence in a nebulous spirit of internationalism, which had gone past its sell-by date; a parochial obsession with internal party politics and personalities; a lowering of the bar for the behaviour of the most malignant actors; a failure to anticipate that one’s enemies could work together to undermine the existing order; and the hope that the storm clouds gathering elsewhere would not blow too close to one’s own shores.

The point about the way in which that world order unravelled before both world wars was that it was a cumulative process. Diplomats chivvied away it at over a number of years at a lower level, but then larger pieces began to fall off with alarming speed. Once the order began to crumble, it was almost impossible to put it back together again. Right up to 1939, many hung on to the idea that the League of Nations and “collective security” was the best means of re-establishing stability. With hindsight, even its staunchest advocates understood that the League had been dead, in effect, from the moment Japan attacked Manchuria in 1931 and nothing was done. Mussolini’s invasion of Abyssinia and Hitler’s expansionism were just nails in the coffin.

The strains on the world order are most obvious in the Middle East. Borders are collapsing and Syria’s conflict is destabilising all its neighbours and Iraq, Lebanon, Jordan and Turkey in particular. There is an arms race and a string of proxy wars – including one hotting up in Yemen – in which Saudi Arabia and Iran are the leading but not sole participants. Yet Russia’s recalcitrance over eastern Ukraine is a symbol of how these things can have a domino-like effect.

Red lines have come and gone. Treaty alliances that once stabilised the state system are now looked at with some trepidation, the most obvious of these being Nato’s Article 5, committing member states to a war in the event that any one of them is attacked. Germany took much the same risk by invading Belgium in 1914 (to whose defence Prussia and Britain had committed themselves by treaty in 1839). At the very least, there are some in Moscow who calculate that Nato’s commitment to preserving the sovereignty of the Baltic states is not so copper-fastened as it once was.

Still, it is in Syria that the echoes of the 1930s are most resonant. In fact, it contains elements of the assault on Manchuria, the invasion of Abyssinia and the Spanish civil war all rolled into one: the failure of international arbitration; the brutalisation and radicalisation of a whole generation; the indiscriminate use of air power against civilian populations; and the use of the country as an ideological and geopolitical battleground for much bigger external forces.

There is also the fear – as was the case with Spain – that it will be a dress rehearsal for a much bigger conflict. The main external powers fuelling it have yet to confront each other face to face.

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Closer to home, another uncanny echo from the 1930s is the incoherence and haplessness of many of those engaged in the British foreign policy debate. One reason why the policy of appeasement went unchallenged was that its critics failed to get their house in order and offer viable alternatives of their own.

The case of the Labour Party in the 1930s provides an interesting story that has lessons for today. Crushed at the 1931 election, losing more than 200 seats, Labour spent much of the next few years in a state of disarray. Its incoherence, faddishness and wishful thinking on foreign affairs were a symptom of this. From 1931 to 1935 the party was led by a grey-haired septuagenarian pacifist, George Lansbury. Within a few years, Lansbury was forced out by the “realists” in the party, such as Ernest Bevin and Hugh Dalton. They understood that Labour would never be a serious prospect for office unless it demonstrated that it was grown-up and tough-minded about world affairs and the British national interest.

Clement Attlee, who became leader in 1935, was in some ways stuck between the “realist” and “pacifist” instincts of the party. Significantly, he thought his leadership role was to be a unifier rather than one whose views were to be imposed on others in the party. Attlee was not blessed with Churchillian foresight. Over the course of the second half of the 1930s, he let Bevin and Dalton fight the battle over rearmament in the party, eventually coming round to supporting the government on the decision to increase military spending.

Yet Attlee carved his own niche in foreign policy in two ways that were to be of long-term significance to the future of the Labour Party. First, he broke from the realists in his party over the Spanish civil war. While Bevin and Dalton believed in non-intervention, in agreement with the government, Attlee visited the front line and demanded that the arms embargo be lifted to allow the Republicans to resist the forces of General Franco. Second, Attlee offered firm opposition to the third strain of thinking about foreign affairs in the party: those who wanted a “Popular Front” against fascism, bringing in all the crackpots of the far left, communists and radicals.

Attlee believed that the tendency to see every foreign policy issue as a left-right matter, or to become the mouthpiece for tyrants, betrayed the traditions of the Labour Party and British democracy. Apologists for Stalinist Russia were treated with contempt. In his view, the most important distinction was not between capitalists and anti-capitalists but between democratic and totalitarian systems of thought. Republican Spain was to be supported because it was a democratic and legitimate government – not because there were communists fighting on one side and fascists on the other. For all its flaws, he believed that the western alliance was the key to world order.

Now, for the first time in its history, it looks like the Labour Party may be led by an odd composite between a special pleader and a Little Englander. What chance will it have of articulating a serious alternative foreign policy, as opposed to “hawking its conscience around” (as Bevin said of Lansbury) from issue to issue? One thing that could at least be said for Lansbury’s pacifism was that it was consistent. He saw the mote in the eye of others, as well as our own.

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The problem with British foreign policy runs deeper than the ructions in the Labour Party. General Sir David Richards, the former chief of the defence staff, is reported to have offered some severe criticisms of the approaches towards both Libya and Syria. He is not the only one to express concern about a current lack of both “strategy” and “statecraft”.

More broadly, British foreign policy has yet to come to terms with the passing of the phase known as “the end of history”. This notion, coined by Francis Fukuyama in 1989, which held that the western liberal-democratic model had triumphed, has been much critiqued. But the truth is that many of those who mock it are still stuck within its parameters. Our response to Syria has been conditioned by the assumption that sooner rather than later the main participants will come to their senses and seek compromise and agreement. Even today, despite many indications of the coming storm, we still struggle to get to grips with the ferocity and barbarity of Islamic State. Sectarianism, ethnic rage and ideology are things we find difficult to comprehend.

Syria has exploded anything that remained of the post-Srebrenica norms. The figures involved alone prove that. It is estimated that between 200,000 and 250,000 people have been killed, with four million refugees and seven million displaced inside the country. The nature of the violence must also be taken into account. In Assad’s treatment of his own citizens, every taboo of the post-cold-war era has been violated. At the same time, the killing rage of IS has outstripped anything the most seasoned jihadis managed during the war in Afghanistan or the Iraqi insurgency. The unthinkable has been normalised.

The yearly ritual of outrage, stern condemnation and expressions of solidarity is repeating itself once again, leading towards another parliamentary debate. We are very fast to climb the podium. Yet the ligaments that link ends and means – the sinews of any viable foreign policy – have been badly torn, if not quite shredded.

Policy on Syria has been largely regurgitated from elsewhere. The most obvious instance of this was the airlifting of the Libya model to the Syrian case. This was the assumption that, once protests against the Assad regime turned into an uprising, Damascus would fall in a wave of democratic protest. This prompted the west to assume the absolutist position that “Assad must go”.

Such moral clarity can be a laudable thing. It is not to be forgotten that Assad has been the chief aggressor in this war, and he, more than anyone, has created the conditions for the rise of IS. But the truth is that this was a posture rather than policy. It was based on the expectation that Assad would follow the fate of Muammar al-Gaddafi, rather than any sense of how this might be brought about. The consequences were twofold.

First, it hardened the resolve of Assad’s sponsors, who were much more willing to take action than the prophets of collapse. Second, it boxed the west into an unrealistic stance from which it could find no firm foundation to exert any leverage.

When it became clear that the situation was not so easily solvable, and that Assad was stronger than presumed, attention should have turned to the humbler aim of trying to manage the conflict down. Instead, the response was to shrug shoulders and give up. In a shift to a putatively more “realist” position, Assad was offered certain “red lines” from within which he would be allowed to conduct his campaign unmolested from outside. When he flouted those red lines, the authority of the west was diluted further still.

Another flaw in the Syria discussion was to have the wrong debate. A conventional intervention was a non-starter from the outset. It was as politically impossible as it was forbidding in practical terms. But under the obsession with “troops on the ground” and “exit strategies” – a rerun of Iraq this time – insufficient consideration was given to other options such as the establishment of a humanitarian corridor, or a “no-fly zone”. Once again, containment, rather than intervention, should have been the overall watchword for the policy.

Another false notion that proved hard to shake was that there was only one of two options available – sticking with the Assad regime as the lesser of two evils, or helping it topple and dealing with the consequences, including IS, later. To have allowed for limited air strikes against the regime’s chemical weapons installations was not to hand the keys of Damascus to IS: it was not, in fact, the leading player in the opposition at that point. A relatively limited, largely symbolic response would probably have prevented the repeated use of the weapons.

These pendulum swings of sentiment have left us with no coherent strategy at all. What we now have is a hotchpotch of different tactics, designed to serve different ends, and some in contradiction to others. The investment in training and supporting more moderate members of the anti-Assad opposition – of whom there were undoubtedly significant numbers – came two years too late to make any difference. The embedding of military advisers with the Iraqi army and some Kurdish forces has been a pinprick exercise that, it is largely agreed, has been under-resourced. The US has struck a deal with Turkey to use its airbases to launch attacks on IS, but Turkey’s contribution to the aerial war has been targeted mostly at Kurdish forces in Syria, rather than IS. Until recently, the Syrian Kurds were the most effective ground force against IS. Their weakening is likely to be costly.

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The most nonsensical of all the strategies at play is the one now promoted by the UK. This has led it to partake in coalition air strikes in Iraq – at the invitation of the Iraqi government – but not Syria, where IS is far more embedded. This was the result of a messy parliamentary compromise made last September, against the backdrop of IS attacks on the Yazidis. It reflected the government’s desire not to be seen to be straying too far from the US; and perhaps the last embers of Labour Party internationalism.

It had been the Prime Minister’s intention to bring the matter back before parliament this month. The Corbyn factor (if he is elected leader) may lead to the postponement of that in the short term. Yet the migrant crisis obliges the government to articulate a new strategy for Syria, sooner rather than later. David Cameron will not permit the Labour Party time to settle in to a new parliament for long, particularly if he continues to take all the heat on the refugee crisis.

The inadequacy of the existing strategy on Syria is clear for all to see. Britain cannot fix the country, and no one is pretending it can. Any escalation of proposed British involvement is likely to be highly limited. It will be mostly symbolic, an effort to show more willing to share the burden with allies such as France and America.

In the US, away from the circus of the Republican presidential contest, there have been more measured criticisms of existing policy. An indication of a potential change of direction was given in a report issued last month by the Centre for a New American Security, a left-of-centre think tank close to the Democratic Party establishment. One of the report’s co-authors was Michèle Flournoy, who was touted as a possible secretary of state under Obama, and who will probably be a favourite for that position if the Democrats retain the White House.

A year after Obama’s offensive began, Flournoy argues that the “current efforts to counter Isis are not adequate to the task” and makes 11 recommendations for a change of policy. Among the most arresting of her proposals are: to give arms to Sunni tribes and the Kurdish Peshmerga; to increase attacks on IS, making more use of advisers embedded with the Iraqi military; and ending restrictions on aid to the Syrian opposition. This is to feed in to what she describes as a “tourniquet strategy” – containing the situation and tightening the grip on the regime as a prelude to fresh efforts to seek a political settlement on the ground. Some uncomfortable moral dilemmas would arise from this. It is likely, for one thing, that the west would become more involved in the proxy game. Neat moral choices are rarely available in such circumstances.

On the refugee crisis, a wider European approach is needed. When it comes to dealing with the Syrian conflict at source, the truth is that any involvement will fall within parameters defined by changes in US strategy. Britain does not have the means or the wherewithal to do anything transformative. The fundamental question that parliament will soon be asked to face is a lesser one: whether it wants to become more involved in shared efforts to manage the crisis and to mitigate its worst aspects (understanding that this might also involve the use of lethal force). The alternative is to hope that others will continue to take care of Britain’s immediate interests.

Of course, one option is for Britain to decide, as Corbyn has suggested, that it is a small island on the north-west coast of Europe and to behave accordingly. This position will certainly find advocates on the far left and far right of British politics. Another option is to accept that Britain has a stake, and an interest, in some sort of world order, and that leaving others to prop it up has not worked out well in the past.

John Bew is reader in history and foreign policy in the war studies department at King’s College London and a contributing writer for the New Statesman

His new book, “Realpolitik: a History”, will be published by Oxford University Press in November. He is completing a biography of Clement Attlee