Were you to listen to some of world’s leaders, you might believe the threat from ­Islamic State has been defeated.

Last week, Russian strongman Vladimir Putin defiantly announced that Islamic State had been vanquished on both banks of the Euphrates River in Syria and that it was time for the political process to take centre stage.

And in neighbouring Iraq, Prime Minister Haider al-Abadi announced last weekend that the war against Islamic State was over.

But the definition of defeat is a contested one and, as we have seen before, politicians are likely to announce the successful accomplishment of combat missions well before military commanders are willing to acknowledge the same.

Regardless of the state of Islamic State in Iraq or Syria, the reality is that in Syria, at least, the defeat of the jihadist group hasn’t made the resolution of the civil war that much easier.

A fractured and fractious non-­Islamic State armed opposition backed by regional states with often conflicting but always self-interested aims; a decisive and committed Iran and Russia; and a US that faced enormous public pressure to stop the killing but with no good or viable options to do so — all have meant that Syria has been a more complex problem than Iraq.

Despite the multifaceted ­nature of the conflict, the backers of Syria’s President Bashar al-Assad would have the public believe the war is nearly won. Before last week’s pronouncement, Putin also had said during a meeting with Assad in Russia late last month: “As for our joint efforts against the terrorists in Syria, this military operation is nearing completion.”

About the same time, Iran’s President Hasan Rowhani said in a televised address regarding the battlefield successes against Islamic State: “Today with God’s guidance and the resistance of people in the region, we can say that this evil has either been lifted from the head of the people or has been reduced … the remnants will continue but the foundation and roots have been destroyed.”

Non-Islamic State fighters still hold territory in the north and south of the country, but the “de-escalation” zones negotiated with significant Russian help have reduced the group’s immediate importance, even though fighting continues in some of the areas it controls, albeit at a reduced level.

Attention therefore has shifted to the future political make-up of Syria. And in that regard the supporters of the Assad regime have been on the front foot, trying to transform the battlefield momentum that has been established in the fight against Islamic State in the east into political momentum at the negotiating table.

In the past few weeks the leaders of Russia, Turkey and Iran met at Sochi in Russia, preceded by a secret meeting the day before between Putin and Assad that featured a well-publicised hug between the two leaders.

At the same time in Saudi Arabia, a meeting of the fractious opposition groups was held, preceded by the resignation of Riad Hijab, the hard-nosed head of the Saudi-backed umbrella opposition grouping known as the High Negotiations Committee.

The new grouping has maintained its demand that Assad needs to step down at the start of any political transition, a demand naturally rejected by Damascus.

There are many sticking points besides the role of Assad in determining the political future of Syria, including questions surrounding the adoption of a new constitution and the nature and eligibility of voters and candidates for UN-supervised elections. There are also fears among anti-Assad opposition groups that Moscow has been encouraging the creation of more pliant groups within areas of Syria to dilute the anti-Assad nature of the long-term political opposition.

Moscow undoubtedly is driving the diplomatic initiative and has gained agreement for a future Syrian National Dialogue Congress involving the Syrian government and unnamed opposition groups in Sochi at a date to be determined.

While the West demands the future of Syria be decided by the UN-sponsored Geneva process, those states with the most skin in the game are trying to provide Geneva with a political fait ­accompli.

Unfortunately, Washington’s ability to shape the post-conflict political structure of Syria is limited; its military partner, the Kurdish-dominated Syrian Democratic Forces, is not a good political ally.

It has fought well, enjoying the type of significant military support that only the US war machine can provide. But it won’t enjoy this type of support forever, or even for that much longer. And, without it, its influence in the post-conflict negotiating process is limited. ­

Certainly the Kurds’ battlefield success means they will be in a strong bargaining position to gain a greater degree of political autonomy than they have enjoyed ­before. But Turkey, Iran and Iraq, as well as the Assad regime, have an interest in limiting their scope.

Turkey’s recent interest in joining the Russian diplomatic push has been motivated by its desire to influence any agreements with the Kurds. And there are reports that the Russians have been making approaches to the Kurds as a way of providing a soft break from the Americans, who they are keen to sideline in any future ­negotiations regarding Syria’s political future.

To be fair, Washington has been consistent in its messaging that its aim in supporting the Kurds was limited to the defeat of Islamic State. And there are signs it is trying gradually to modify, if not disengage, from its relationship with the Syrian Democratic Forces. The White House says Donald Trump, in a recent telephone call with Recep Tayyip Erdogan, informed the Turkish President of “pending adjustments to the military support provided to our partners on the ground in Syria”. The Turkish government’s ­interpreta­tion of the call was that Washington had given clear instructions to the Kurdish-led SDF that it would receive no more weapons. The possibility of weapons given to Syrian Kurdish groups finding their way into the hands of Turkish Kurds has been a concern for the Turkish government.

Indeed, in June, US Defence Secretary Jim Mattis promised his counterpart that inventories of weapons given to Syrian Kurdish forces would be passed on to Ankara and that all weapons ­issued would be taken back by Washington after the defeat of ­Islamic State. Realistically, though, it is almost impossible to account for all weapons and ammunition issued to combat units unless you have quartermasters in every SDF unit.

There will likely be an ongoing US military presence for some time. There is a valid argument that pressure needs to be maintained on the pockets of ­Islamic State that continue to exist east from Deir Ezzor to the Iraqi border and that may contain senior members of the terrorist group.

There is also a line of thought that humanitarian groups would rather deliver their aid under a US security umbrella rather than having to be seen to dance to Damascus’s tune.

The truth is that both these outcomes ultim­ately would serve Assad’s aims.

Assad doesn’t have the financial resources to pay for reconstruction, so any international help he gets will be to his advantage. He understands that whatever limited governance structure Washington sponsors in Raqqa or other areas will have a shelf life equal to the US military presence. In other words, it will be limited.

It is difficult to establish what kind of negotiating leverage a limited and isolated US presence in the northeast gives Washington.

Burdened with an imprecise strategic aim, an uncertain legal basis and surrounded by enemies who know their presence will be time limited is potentially a recipe for disaster. Similar conditions faced a smaller number of Western coalition and Syrian partner forces in the southeast of the country near the Tanf border crossing with Iraq earlier this year.

The practical challenges posed by occupying Syrian territory while Syrian and Iranian-backed militias operated outside, adjacent to or even within the self-declared “exclusion zone” was on show and their limited freedom of action and uncertain role should have served as a salutary lesson for those who promoted a similar, if much larger, version in the northeast.

And if the US’s bargaining position regarding future Syrian political structures was marginal already, last week’s announcement by Trump that Washington recognised Jerusalem as Israel’s capital didn’t help things.

Although the practical ramifications of the announcement are minimal, the symbolism isn’t. And in a region where symbolism often trumps substance in moulding popular opinion, the announcement simply reinforced in many people’s minds that the US in general, and this administration in particular, is more interested in promoting Israel’s political interests than it is in advancing democratic norms in the Arab world. As a consequence, perceptions such as these make diplomatic initiatives proposed by Moscow appear more appealing than those ­advanced by Washington.

With this in mind, the US would be better off limiting its strategic aim in Syria by focusing on ways in which it can effectively blunt an expanded Iranian presence in Syria. In some respects, though, the horse has already bolted. Damascus is financially indebted to Tehran for billions of dollars in lines of credit, and economic agreements in mining, agriculture and telecommunications have already been inked between the two countries. And the Syrian media has reported that Assad and Rowhani agreed in a recent telephone call that Iran would be a partner in Syria’s reconstruction.

Iranian Revolutionary Guards Corps-affiliated companies can easily provide an Iranian footprint in Syria under cover of commercial activity, even after their combat troops and those allied militias have left Syrian soil.

The Russia, Turkey and Iran triumvirate appears to be dictating the pace and direction of discussions regarding Syria’s future. But there are opportunities for Washington to exploit the differences that exist between these strategic actors. Moscow, Ankara and Tehran are not natural partners. Separated by ethnicity, religion, history and political systems, theirs is a tactical alliance of convenience.

Memories of the Russo-Persian wars two centuries past that stripped much of the Caucasus from Persian control and the 1941 Anglo-Soviet invasion and occupation of Persia exist not far below the surface. Moscow also held Ankara’s feet to the fire when a Turkish aircraft downed a Russian Su-24 in 2015, killing a Russian crewman. And Ankara and Tehran relations often have been marked by tensions over differing policy approaches towards Syria, Yemen and Israel, to name a few.

If Washington wants to concentrate on limiting Iranian influence in Syria after the defeat of Islamic State, then it will most certainly need Russian and Turkish help. Turkey has a 900km border with Syria and its commercial contacts with northern Syria are extensive. Russia has more than a half-century of security and trade links with Syria and is an acceptable, long-term foreign presence in the country.

But Moscow and Ankara desire stability in Syria, as well as access to international reconstruction funds to maximise their post-conflict economic returns. If Washington wants to shape the post-conflict environment in Syria to limit Tehran’s influence there, then it should seek to use the self-interest of two of the triumvirate to isolate the third.

This may require some unpleasant policy decisions such as a private acquiescence to Assad’s continuing presence in the interim and access to funds from wealthy Gulf entities in return for a clearing of pro-Iranian groups from the Israeli border region and a freezing of any further Iranian commercial presence in Syria, for example.

None of these options may appear palatable at first glance, but when one is in as weak a bargaining position as Washington, it is appropriate to acknowledge it and distil exactly what the main strategic outcome Washington desires and how best to achieve it.

The Syrian civil war appears to be entering its final phase, and if Washington and the West want to be in a position to shape the outcome to their advantage, or even to limit negative outcomes, some pragmatic but unpleasant policy decisions will have to be made.

Washington has always appeared to be on the back foot because it lacked leverage and a coherent strategic aim. In contrast, by viewing the issue in simple ­binary terms, Russia and Iran were able to establish a simple aim and commit resources towards achieving it.

But in post-conflict Syria, it is difficult to see the Moscow-Ankara-Tehran axis holding together in the long term because of their differing strategic aims. Any leverage that Washington is likely to possess in Syria is likelier to come from exploiting these differences than it is from holding ground with the Kurds in northeastern Syria.