What of the economic consequences of an escalation of war in Syria? I say "escalation", of course, as civil war has raged across this blighted nation for the last seven years.

Smaller than the UK, with an official population of just 20 million, Syria has been imploding since the 2011 Arab Spring.

That regional uprising unleashed pent-up domestic frustration with the authoritarian president Assad - long guilty of rigging elections and incriminated by the United Nations for war crimes.

Ever since, an uneasy coalition of contrasting militia - from Islamists to Kurds, from extremists to secularists, some US-backed but their alliances constantly shifting - have tried to oust the dynastic president, in office since the turn of the century.

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It was the chaos of civil war, and the ensuing power vacuum, that allowed Islamic State of Iraq and the Levant to make gains and impose its barbaric rule in Syrian strongholds like Raqqa.

That threat, on the back foot for now after intervention by a Nato-led coalition, remains ever present.

Having launched airstrikes against Assad's enemy,the West has now moved to act against Assad himself.

This weekend, the US, the UK and France responded to evidence that the Syrian government launched chemical attacks in Douma by ordering a coordinated airstrike on three facilities in the country.

Whatever happens in the aftermath of the strikes, this Syrian war already represents a human tragedy of near-biblical proportions.

Upwards of 700,000 civilians have been killed, say the UN, with an estimated 13m displaced - over half the population.

And, of course, the Syrian economy has been wiped out too.

The damage in terms of destroyed infrastructure and lost growth has already cost Syria a colossal US$226 billion ($307b), according to a 2017 World Bank report - an amount several times the nation's entire GDP back in 2011.

If that sounds like a meaningless calculation, consider that, beyond the death tolls, more than three-quarters of all Syrians of working age are unemployed - an economic calamity that will massively impact skills, dragging down future growth too.

The collapse of basic amenities and the health sector is also having devastating consequences, with the World Bank concluding more have died from medical failures and disease than from bombing and other military activity.

What is really taxing the minds of international investors, though, is the potential impact of Western airstrikes, and related heightened violence across the Middle East, on stocks, bonds and currencies.

Equities have long looked overvalued and fragile. Could this weekend's events spark a market meltdown?

We're living in a world where global markets are being led largely by the White House.

Countless billions of dollars of transactions are now driven daily by Trump's cyber-utterances on tariffs against China, on sanctions against Russia and now signs of his thinking on airstrikes.

Last Wednesday, when the US president implied in a tweet that a missile attack on Syria was imminent, the Dow Jones Industrial Average, the bellwether US stock index, fell a hefty 220 points.

The next day, a fresh Trump tweet sounded less gung-ho - "Could be very soon or not so soon at all!" - and markets bounced back.

Traders Robert Charmak, left, and John Panin work on the floor of the New York Stock Exchange. Photo/AP
Traders Robert Charmak, left, and John Panin work on the floor of the New York Stock Exchange. Photo/AP

This weekend's intervention comes at a time when Investors are already trying to price in a bewildering range of moving policy parts.

President Xi last week discussed plans to lower China's import tariffs on products, including autos - clearly a positive development.

The minutes from the March meeting of the Federal Reserve's open market committee showed that "all" members see the US economy growing at a strong pace, but are concerned about inflation too.

That makes earlier, larger interest rate rises more likely.

And now, eyeing the Middle East from afar, many traders who until recently couldn't find Syria on a map must now weigh a situation where one person's conspiracy theory is another's vital insight.

What do the Russians really want - apart from access to their Syrian warm-water ports?

Can this situation de-escalate without Moscow's help, given Russia's influence in Damascus? Will Iran, that other regional power broker, do what Vladimir Putin says? Can the Islamic Republic be engaged without riling Israel?

Isn't this war really about rival pipeline-building schemes, sponsored by competing Gulf exporters, to transport gas across Syria and on to Western Europe?

Is that why Moscow is stirring things up - because, as Europe's main gas supplier already, Russia doesn't want Gulf gas moving across Syria.

As outlandish opinions swirl - the Douma chemical attack was a "false flag" operation by the West, apparently - rational analysis is giving way to rumour.

Trading floor veterans are telling themselves that, for all the diplomatic angst and human fallout, military strikes typically have limited market impact.

While that's true, this crisis could mark a turning point for oil. Last week's tensions saw Brent Crude spike above US$72 - its highest level since 2014.

Syria isn't a key producer, but the wider region is obviously the world's most important oil exporter.

Saudi Arabia wants oil higher, before it sells a chunk of the state energy giant Aramco next year.

With spiralling welfare bills, and dwindling cash reserves, Riyadh needs the cash.

So, if strikes on Syria cause oil to rise further, the Saudis could ride that momentum, using the Opec exporters' cartel to further limit supplies and push oil still higher.

The economic impact of US$80-plus crude would ripple across the globe - having started in Syria.