Iain Duncan Smith is a former Secretary of State for Work and Pensions, founded the Centre for Social Justice, and is MP for Chingford and Woodford Green.

In the early hours of 7th April, 59 US Tomahawk missiles smacked into the Syrian-controlled airbase at Homs, in retaliation for the chemical attack which killed more than 80 civilians, many of whom were young children.

The attack didn’t just wreck the airfield and some ten per cent of the Syrian Airforce; it also, at long last brought an end to Obama’s weak and indecisive policy in the Middle East – a policy characterised by the Sunday Times as an era of ‘New World Disorder.’ That era left a vacuum into which Russia stepped, aided and abetted by its two most unsavoury allies: Iran, (the main sponsor of terrorism in the Middle East and the wider world), and the out-and-out terrorist group, Hezbollah.

The vacillation over the last few years by the Obama White House amounted to a sorry saga. After two years of indecision, starting with Assad’s rebuff of Obama in 2011, Russia’s veto of action in the Security Council in 2012 and finally Assad’s flaunting of Obama’s red line over the use of chemical weapons, Obama finally decided to act.

However, instead of taking swift action, after much public speculation the UK was asked to join him in attacking the Syrian Command and Control centre. I well remember how we discussed the plan for the air strikes in Cabinet, yet afterwards Parliament rejected the operation. I was sorry that, notwithstanding some of the legitimate concerns raised, Parliament overall rejected our involvement.

None the less, to my astonishment, instead of going ahead on his own, Obama, seeking a way out, weakly clutched at a Russian plan to get Assad to hand over his chemical weapons. In what seemed desperation and not a little impotence, Russian assurances were far too readily accepted, and the USA quit the field to the Russians, whilst hurriedly proclaiming this to be a good deal.

Now, after those Russian assurances are shown to be worthless, and motivated by terrible pictures of families dying agonising deaths after being overcome by sarin gas, Donald Trump and his team decided to act. This action brings the USA back into the region with a clear show of intent, at a time when some 400,000 people have died – of which at least 200,000 were civilians – and 10 million have been driven from their homes.

As the dust settles and we all take stock, asking what the West should do next, there will be an inclination to see this in the narrower context of the Syrian conflict alone. I believe that would be a mistake.

We only need to look at Iraq to realise how the Syrian conflict has tipped over into neighbouring states. Iran’s enormous influence over the predominantly Shiite government in Iraq, and their support for Assad, led directly to the creation of ISIS and their bogus caliphate, made up of hugely disaffected Iraqi Sunnis. Now, as Mosul slowly gets re-taken by the western-backed Iraqi forces, there arises the enormous question of what should replace the chaos left behind. This is why the USA’s re-entry into the arena isn’t a moment too soon. For as we degrade Isis’s capability, we must also be concerned not to let Iran and Hezbollah fill the vacuum.

Rex Tillerson’s upcoming visit to Moscow is vital, not because it will produce a sudden settlement but because, coming as it does after such an emphatic statement of intent by the USA, it means the Russians know they will have to deal with the US or there can be no settlement. After all, Russia’s problems are as clear as its objectives. Russia is reliant on oil, and the low oil price has left the economy in dire straits. Worse, it now has to support costly interventions in Crimea, Eastern Ukraine and Syria. Yet Putin cannot afford to lose face after all his sabre-rattling and military intervention. This is why his objectives are also clear; he knows that the Russian people need to see Russia with its reputation intact. To do all of this, they must hang onto the warm water port they now occupy in Syria. The only way, at present, they believe this can be achieved is to have Assad in power.

I happened to be in Washington finishing up a couple of days of discussions with Senators and Congressmen on Capitol Hill before and after the Tomahawks hit. I was struck by the strong level of support for Trump on all sides of the political divide. It seemed to me that there was almost a collective sigh of relief from them all, because after all that Russia has been up to, and with questions over the administration’s attitude to it, the new President had sent a strong signal to that the USA is back and prepared to act.

However, others went further and made it clear that this action alone will not be enough. The USA must now make it clear to the Russians that their support for Assad makes them complicit in his use of chemical weapons, and they now need to think again about that continued support.

Finally, beyond Syria and the Middle East, it can’t have escaped anyone’s notice that this decisive action is likely to have had another effect as well. President Xi was dining with President Trump at the time of the missile strike, and he will have been left in no doubt that Trump’s earlier warning to the Chinese about North Korea was a serious statement of intent. They will recognise the urgent need to act over their dangerous neighbour as well.