LAST month while on the Lebanon-Syria border, I was told the sad story of a young Syrian mother named Fatima.

Along with her extended family, Fatima had fled the fighting in her city. Together they had walked for six hours before the young woman made the fateful decision to turn back alone to retrieve the passport and ID cards forgotten though panic while escaping the shellfire and marauding gunmen ripping their neighbourhood apart. Fatima made it all the way back to her living room, before a sniper caught her in his rifle's crosshairs and dispatched the bullet that killed her.

As a mother, Fatima had known all too well that the documents would be needed if her family were lucky enough to make it across the border to join the millions of other Syrians who had come before them to face life as refugees in Lebanon.

As 2013 draws to a close, the UN ­estimates that almost 2.3 million Syrians have fled to neighbouring countries such as Lebanon, Jordan and Turkey since March 2011. Those displaced within Syria itself, meanwhile, are thought to number as many as 6.5 million.

It is a humanitarian crisis of ­colossal proportions. Syria's civil war may have its origins back in 2011, but it is the ­catastrophic events of the last 12 months that have led to a dramatic increase in the numbers of civilians caught up in this conflict.

It was barely a year ago this month that the United States joined Britain, France, Turkey and Gulf states in formally recognising Syria's opposition National Coalition as "the legitimate representative" of the Syrian people. Since then the country's conflict has intensified with a scarcely believable savagery.

Personally, I have always been wary of terms like the "international norms of war" used by human rights observers. In almost three decades of covering conflict, I have seen precious little evidence that any war has such "rules". But if one thing does mark out Syria's current conflict, it is the way all sides in this no-quarter struggle flagrantly flout human rights and the notion of innocent civilians as noncombatants.

A macabre marker for the year ahead was laid down in January, when 65 bodies were found in the bitterly contested northern city of Aleppo, many of them bound and shot execution-style. Throughout February, rebel advances were put down to a surge of weapons said to be supplied by outside powers arming so-called moderates within the Free Syrian Army. Yet by March, the Islamist al-Nusra front was becoming dominant in many rebel-held areas. As the battlefield stakes increased, accusations surfaced that the Syrian regime was using chemical weapons.

The dangers of such an escalation and the conflict's capacity to spread regionally were further underlined when Israeli warplanes targeted a Syrian facility that housed Fateh-110 missiles, which may have been destined for the Lebanese Shi'a militant group Hezbollah.

Certainly by May, Hezbollah, a long-standing ally of Syria, was sending thousands of its men to support President Bashar al-Assad's forces and fight against the rebels in parts of the strategic border town of Qusair.

Partly in response, the European Union decided to lift the arms embargo on the Syrian opposition while maintaining all other sanctions against Assad's regime. The move came too late, however, to help prevent regime forces capturing Qusair after months of heavy fighting.

By now the UN estimated the ­growing violence had killed as many as 93,000 people, while US officials concluded that the Syrian government was undoubtedly using chemical weapons.

It was on August 21, however, that this conflict reached what many regarded as a tipping point, when Assad's regime launched a deadly chemical attack on Ghouta in the suburbs of Damascus, violating international regulations and inciting worldwide outrage.

Horrific television reports showed victims crammed into makeshift hospitals with hundreds of them convulsing and gasping for breath. UN chemical weapons inspectors sent to investigate the attack themselves came under sniper fire while trying to access one of the affected towns. A subsequent US ­intelligence assessment of the strike concluded it had killed 1429 people.

The world braced itself as US President Barack Obama spoke of the Syrian regime having crossed a "red line" and weighed a military strike against Syria that would be of limited scope and duration. Obama said the US had a moral responsibility to respond forcefully but that he would not do so until Congress had a chance to vote on the use of military force.

It was a diplomatic standoff between Syria and the United States that had the world holding its breath at the prospect of another potentially disastrous major military intervention in the Middle East. Enter stage left Russian President Vladimir Putin. In what many saw as a face-saving lifeline for Washington in the push for Syria to surrender chemical weapons, the Russian foreign minister, Sergei Lavrov, announced that Moscow was "calling on the Syrian authorities not only to agree on putting chemical weapons storages under international control, but also for its further destruction and then joining the Organisation for the Prohibition of Chemical Weapons". In what many saw as a shrewd diplomatic manoeuvre by Moscow, direct Western intervention in Syria was brought back from the brink.

Perhaps sensing this shift, UK MPs rejected military intervention, with Prime Minister David Cameron saying he would respect the defeat of a government motion by 285-272, ruling out joining US-led strikes.

By September, President Obama also came under domestic political pressure and put military action on hold, vowing to pursue diplomacy to remove the Syrian regime's chemical weapons. It was a step back from the abyss given that later that month a UN weapons inspectors' report found "clear and convincing evidence" that rockets containing the nerve agent sarin were used in the attack on Ghouta.

Since then, however, Assad has allowed international inspectors to begin destroying Syria's chemical weapons on the basis of a US-Russian agreement, with the regime subsequently declaring its chemical weapons production facilities inoperable.

For the time being an international escalation of the Syrian conflict had been averted, but the situation on the country's battlefields has continued to worsen. A few weeks ago, 11 of the biggest armed factions repudiated the main Western-backed opposition coalition and announced the formation of a new alliance dedicated to creating an Islamic state in Syria. More recently, those same Islamist groups' ­territorial and strategic victories forced the US and Britain to suspend "non-lethal" support for rebels in northern Syria. And so the war rumbles on.

The biggest worry for the coming year is the burgeoning humanitarian fallout. So bad is the plight of those Syrians displaced by the fighting that the United Nations has announced its biggest ever appeal, seeking £4bn for humanitarian aid to Syria. The international body estimates that nearly three-quarters of Syria's 22.4 million population will need humanitarian aid in 2014.

With bread prices having risen by 500% in some areas, four out of five Syrians now say their greatest worry is that food will run out. They also face the ravages of the recent storm named Alexa, which has brought heavy snow, hail, driving rain and icy winds to the region, with the Bekaa Valley in Lebanon particularly badly hit. In the days before I left the ­refugee areas on the Lebanon-Syrian border, snow was already beginning to fall, as were the temperatures. As the winter weather takes its grip, hope of any respite in Syria's civil war seems as distant a prospect as ever.

The children left behind by Fatima, the young mother killed by a sniper, face an uncertain future, and the lives of millions of Syrians have been irrevocably changed by a conflict with no end in sight. How many more will face a similar fate before sense prevails?