The former rebel stronghold of Qusayr is described by reporters as a "ghost town" after three weeks of devastating assault by the Syrian army and its allies from Hizbollah, the Lebanese Shiite militia.

It is tempting to imagine that one of those ghosts is that of Sir Mark Sykes, the British adventurer and politician who helped to draw the borders of modern Syria, ushering in almost a century of instability.

Sykes is no stranger to an unquiet grave. Five years ago, his lead-lined coffin was opened at the request of scientists who wanted to see if his body contained the virus of the influenza pandemic of 1918-20. Sykes fell victim to the flu in 1919, one of 50 million fatalities worldwide. Researchers thought the virus might have survived inside the lead carapace, which would enable them to discover more about its extraordinary potency.

The mortal remains of Sykes are now underground again. But his legacy is more than ever under the spotlight as his work seems to be unravelling under the pressure of the Syrian civil war.

The carve-up of Greater Syria, then part of the dying Ottoman Empire, started in 1916 in a secret agreement between Sykes and his French negotiating partner, François Georges-Picot. The division began with Sykes drawing a line across the map, from the "e" in Acre (now in northern Israel) to Kirkuk, in Iraq. By the time postwar arrangements took effect, and after some modifications to the line, everything below it line would be British, enabling London to connect its interests in Egypt, across the Suez Canal, to Palestine and Iraq to the Gulf and on to India. Everything north of the line - modern-Syria and Lebanon - would go to France.

This agreement lives in infamy as one of the last gasps of the imperial age. Before the First World War, empires were the governing principle of world politics. In 1917 as the US entered the war its president, Woodrow Wilson, proclaimed an era of popular sovereignty. People should have the right of self-determination. But that did not happen for the people of Greater Syria.

After the secret carve-up was discovered in Russian archives by Bolshevik revolutionaries there, France and Britain needed to find some local or international justification for their land grab. The French created a state for Christians, which became modern Lebanon. Britain set about creating a national home for the Jews, in Palestine. From these two enterprises arose what will soon be a century of instability.

When Sykes's coffin was opened, he was described in the British press as relic of history, but that is hardly true today. The war in Syria, and the intervention of neighbouring governments and foreign fighters, is raising the question of whether the settlement based on the Sykes-Picot accord is tenable.

The battle of Qusayr has intensified that debate. The army of President Bashar Al Assad was able to retake the town only thanks to the help of a sectarian strike force of Lebanese Shia Muslims under the banner of the Iranian-backed Hizbollah. This naked intervention by Hizbollah can only raise sectarian tensions in the organisation's home state, Lebanon. Meanwhile Iraqi Shiites are flocking to Syria to defend religious shrines from the threat of attack by Sunni Muslim jihadis. Jordan lives in fear of the jihadi militias turning their guns on the Hashemite monarchy.

At the same time, the collapse of Baath party rule in Syria and the weakening of the Iraqi state have encouraged the Kurds in both countries to stake claims to run their own affairs. The Kurds were the great losers in the post-Ottoman settlement, which left them divided among Turkey, Iraq, Syria and Iran.

It has long been accepted that the Sykes-Picot borders are artificial, but many thought that given realities on the ground, they might gain acceptability. Now the opposite is happening. National identities are weakening while sectarian ones are strengthening.

There are many reasons for the break-up of Syria. A simple one is that even the most unlikely country can be held together by a wily, ruthless leader such as Hafez Al Assad, father of the current president, but may fall apart under the incompetent guidance of his son.

The idea that Al Sham - meaning both the city of Damascus and Greater Syria, from the Turkish border in the north to fringes of the Arabia desert in the south - as a territorial whole never died in the popular imagination. But what does this mean? Even if the Sykes-Picot deal is generally accepted as a mistake, it is a jihadi pipe-dream to imagine that the clock can be turned back to 1914 and Greater Syria resurrected as a multi-sectarian whole. That would require models of federalism and multi-confessionalism which have yet to be created in the region.

A more likely outcome is that Syria will become a patchwork of warlord fiefdoms, with Mr Al Assad the biggest warlord of them all, seeking to weaken and manipulate the others, with the support of Iran.

The Kurds' dreams of a united state will crash against Turkish nationalism, and against the cautious aspirations of the Kurdistan Regional Government in Iraq, which seems content to advance its self-rule from Baghdad step by step.

Turkey will no doubt seek to coordinate the various Kurdish regions, within its borders and beyond. Can the unwieldy state of Iraq continue with its current borders? The answer could be yes. Iraqi Sunnis do not want to be ruled by the Al Qaeda-linked jihadis in eastern Syria, after the bitter experience of the people of Anbar province until they rebelled in 2006. The Iraqi Shia do not want to be subsumed into Iran.

So the borders may remain, on paper, even if they are increasingly porous and if the central authorities lose the ability to extend their power to their frontiers.

As for Sykes, his lead coffin has proved as disappointing as his lines on the map. When unearthed, the coffin was found to have split. The body, which ought to have been well preserved, was badly decomposed.

aphilps@thenational.ae

On Twitter @aphilps