War is a contest of wills. Although determination alone does not guarantee victory, its absence makes defeat all but inevitable.

Daesh (so-called Islamic State) is an extreme Sunni organisation that has declared a ‘caliphate’ in parts of Iraq and northern Syria. It broke with Al Qaeda two years ago. It consists of about 20,000 fighters, although some sources put its size as high as 50,000. It occupies an area in Iraq and Syria about the size of Britain.

It is the best-funded terrorist group in history, with millions of dollars from oil sales and extortion, ransoms and bank robberies. It can claim to have terrorist hit-squads in a dozen countries stretching from Tunisia to Pakistan. It has affiliated militant groups in about 11 countries, including Nigeria and Russia.

What is sorely needed now is an effort to distinguish between the fate of Iraq and Syria, and the dangers posed by Daesh to the West. The West’s policy has been riven by contradictions and characterised by a lack of commitment and a state of denial about the threat. The West has a strong interest in addressing the latter. Any sound policy response must begin by gauging that threat.

Daesh does not pose a threat to the West in the way that the 20th century totalitarian regimes of Nazism and communism did. Despite its appeal to an alienated fringe, radical Islam cannot compete effectively with the West.

Yet, there are undoubted parallels between Nazism and Islamism. Rather like Hitler exploited the humiliation of Germany at the Treaty of Versailles, so Daesh plays on anger at western foreign policy to win support.

The parallel with the 1930s is that military intervention may be an essential component of the West’s fightback. There will be many who, like Neville Chamberlain, have no desire to go to war “because of a quarrel in a faraway country…”.

But what is happening in Syria is no longer a distant war. Every day, lives in Europe are directly affected by the growing refugee crisis. At some point – perhaps when Daesh carries out, or inspires, a large-scale terror attack in the US or – more likely – Europe, people will look back and say: “Why did the West let that happen?”

The threat posed by Daesh is threefold. First, there is the cultural threat arising from its mindless assault on antiquities and heritage. Secondly, there is the humanitarian threat – for example, the vicious murders of those captured by Daesh or the enforcement of draconian medieval rule. Sadly, as with the assault on cultural antiquities, the attack on human rightselicits a lot of hand-wringing from the West, but no retaliatory action.

The third threat is the one that matters. The West has a profound interest in international order, in a world based on nation-states abiding by certain basic norms of behaviour. Europe, above all, embodies such an order which, while not Utopia, offers at least stability, order and decency.

Daesh is bent on destroying the nation-state system. It is a toxic death cult. You cannot negotiate with fanatics or reason with suicide bombers. Presently targeting Syria and Iraq, it harbours ambitions that go much further afield, stretching throughout the Middle East and beyond.

Western powers must be prepared to respond to calls for greater air support and the limited use of special forces

Western countries (primarily the US, Britain, France and some NATO allies) have the weaponry and military expertise to smash Daesh. But political will and ambition are lacking. After the experiences in Iraq and Afghanistan, the West is reluctant to be dragged into another military quagmire.

If military action against Daesh is to be successfully pursued, it will only make sense if it is well embedded in a broader political and military strategy. The Western response to the threat of forging a coalition of nations committed to establishing stability in the Middle East and destroying Daesh is the first step. A year ago, representatives from several important countries converged on Paris to declare their backing to recapture all Daesh-controlled areas “by any means necessary, including appropriate military assistance”.

It was the right response, but the much trumpeted war against Daesh remains fitful and unfocussed. It has made only halting progress. The West is right to concentrate on building international and regional partnerships. But it must have the will and patience to commit to them over time.

One of the most difficult things to judge in a conflict, such as that against Daesh, is when to move from defensive containment to an offensive strategy. Even harder is summoning up the political will to execute it.

It may be tempting to stay out ofthe fray for a little longer and to think that this will somehow make any future attack easier. This is the challenge now facing the coalition against Daesh and its extremist affiliates.

A Middle East-led air campaign is under way and is increasing its targeted bombing against the Daesh leadership in Syria. There is greater awareness that the spread of Daesh-inspired terrorism must be checked if other countries are not to be similarly destabilised.

The time for major military western allies positively to consider the use of limited ground forces has come. Air or drone strikes on their own, or the provision of trainers and advisers, are no substitute for effective ground troops. These should not be large-scale, conventional armoured forces because the threat from Daesh does not warrant them.

But elite special forces, airborne and marine forces are required. They have been requested by Middle East partners. The West should now be prepared to take the risks required to help its allies to exploit the situation and the new mood in the region.

As to who should lead this battle, the 1916 Arab revolt against the Turks, in which TE Lawrence (“Lawrence of Arabia”) played a significant role, offers the model: “Hide your own mind and person… It is their war, and you are there to help them, not to win it for them”. It is not the West who should lead this battle, but the Middle East members of the coalition.

Regional powers should take regional responsibility. But western powers must be prepared to respond to calls forgreater air support and the limited use of special forces.

If the West calls on Arab states to take up the fight against Daesh, then it also has to be involved. Airstrikes and elite special forces can change battlefield outcomes. It is in the West’s interest that Daesh should be destroyed.

Alternatively, the moves being made by Russia for the West to team up with President Assad to smash Daesh together are politically risky but not entirely fanciful. The defeat of Daesh is only possible with the help of a sophisticated ground army. The only one available – albeit now onthe back foot – is Assad’s Russian-equipped force.

The most pressing dilemma is whether to start cooperating with Russia and Assad in the fight against Daesh, or to continue to ignore the existence of his regime while supporting other regional powers – essentially Saudi Arabia and Turkey – with selected ground troops and air power in a broad anti-Daesh coalition.

As always in the Middle East, options are fraught and finely balanced.

But Daesh is the common enemy. And it must be defeated.