Just months later, world leaders found themselves responding to similar events in neighbouring Syria as claims emerged last week that President Bashar al-Assad had unleashed a massacre whose only brutal precedent was that by the Iraqi dictator in 1988.

Graphic images from the town of Ghouta on the outskirts of the Syrian capital, depicting hundreds of people dead or dying from a poison gas, were quickly likened to the scenes from Halabja decades earlier.

So too estimates of up to 1400 deaths from inside Syria, where Doctors Without Borders reported 3000 cases of neurotoxicity in just three hours and which confirmed the chemical attack as the largest since Halabja. Yet with American, British and French leaders making a hasty push for military action to ''punish'' the Assad regime before the week's end, the international scale and possible global ramifications of the response to Syria look set to far outweigh the reticence of 1988.

''This attack was a game-changer for sure,'' says Andrew Tabler, a senior fellow and Syria expert at the Washington Institute for Near East Policy. ''The chemical weapons use has implications in Syria, the region, and globally.''

The audacity of the attack of August 21 was magnified by its timing, coinciding with a visit by UN inspectors to investigate the alleged use of chemical weapons in the country's 2½-year-old civil conflict. The Assad regime has repeatedly denied any role in the event, attributing responsibility to rebel factions in the area. However, most Western leaders were, as British Prime Minister David Cameron stated, left in ''no doubt'' the regime alone possessed capabilities for such an assault.

The large-scale atrocities at Ghouta reflected a breach of what the Obama administration last year deemed a ''red line'' in Assad's campaign of repression against the internal opposition that has already seen more than 100,000 Syrians killed and 2 million flee the country.

On Monday, the US President had vowed to hold the regime accountable for its ''indiscriminate slaughter'', with Secretary of State John Kerry confirming America's intentions to retaliate against a ''moral obscenity'' that had ''shocked the conscience of the world''.

However, voices from the Syrian opposition, long critical of the inertia of the international community, say the latest atrocity should come as no surprise to Western leaders.

''Everyone in Syria expected this attack,'' says Syrian exile Radwan Ziadeh, director of the Washington-based Syrian Centre for Political and Strategic Studies. ''Western governments were just playing a game of cat and mouse with the regime all this time. They did nothing when Assad started using long-range missiles, and when the small-scale use of chemical weapons was confirmed by all nations there was still no response. So Assad was basically given a green light to use them on a larger scale.''

Originally from the region neighbouring Ghouta, Ziadeh says the systematic cutting-off of medical and food supplies to the area for months before the assault served as an indication such an attack was imminent. ''The town had been under siege for almost three months. The lack of supplies was part of the reason the number of people killed was so high. So it was not only shock we felt at this massacre, but also that we had been abandoned by the international community who let Assad do this. We wondered how many people killed is enough? Will it only be when the whole of Syria is destroyed?''

With this week's announcement that the US military is ready to launch strikes against Assad, followed by Cameron's drafting on Wednesday of a UN resolution authorising ''all necessary measures to protect civilians'', the question of intervention in Syria abruptly become one of how soon, and not if.

As Tabler notes, this tough new stance of intolerance on chemical weapons reflected a marked drive to shake off the ''black mark'' the Syrian crisis has left on Western foreign policy records such as Obama's.

The long-standing sense of indignation among Syrians at the perceived Western indifference of foreign governments was this week reflected in protest slogans and banners from inside the country stating, ''Dear Free World: enjoy watching us burn'', ''Shame on you international community, Syrian people are not numbers'' and ''F--- your red lines Obama''.

Others in the Syrian opposition have argued escalation of the conflict to such violent extremes might have been forestalled by earlier, more proactive policies from abroad. Since the outset of protests in February 2011, the regime has received unwavering political and military support from its allies Russia and Iran, as well as an open supply of arms and combatants from across the border from the Lebanese militant group Hezbollah. The more recent infiltration of forces from Qatar, Saudi Arabia and Turkey, under the aegis of various Islamist and other insurgent rebel factions, means that in the eyes of many Syrians, there has already long since been de facto foreign intervention in their struggle.

By contrast, the largely secular and peaceful elements once at the forefront of the democracy uprising have been left relatively unaided. ''The Syrian people could have done this by themselves and toppled the regime months ago,'' says Walid Saffour, British representative of the Syrian National Coalition, the most prominent international opposition alliance. ''But the continuous and massive support from the Iranians and Russians tipped the equation to the side of the regime. At the same time, the Syrian people were promised a lot, but received very little from the West.''

Bordering Israel, Lebanon, Turkey, Iraq and Jordan, and with strong ties to Iran and a staunch pro-Palestinian platform, Syria under the Assad regime has been a nexus in regional political feuds. Like other commentators, Saffour argues that strategic interests and anxieties over regional instability in the Middle East have paralysed those Western governments who came to the aid of Libyan rebels in the NATO campaign of 2011.

Warding off charges of opening a Pandora's box, Western proponents of intervention have emphasised the narrow scope of their ambitions, with Downing Street reinforcing that any action must be ''legal and specific to the chemical weapons attack''. Unlike the outcomes of the intervention in Libya, or the large-scale ''war of liberation'' in Iraq in 2003, aspirations of regime change in Syria have been explicitly ruled out. Despite this, the obstacles and risks attending even a limited form of intervention are palpable.

Efforts to secure UN backing for any anti-Assad campaign from the five permanent members of the Security Council are expected to be blocked by Russia and China.

Sobered by the political realities, Western leaders acquiesced to UN Secretary-General Ban Ki-moon's plea to allow time for the weapons inspectors to submit findings from their mission, which ends Saturday.

Speaking on Wednesday, Ban said that the Syrian conflict had reached a ''most serious moment' and urged leaders to ''give peace a chance''.

Despite the smaller-scale objectives claimed by London and Washington, memories of the political deceit behind the Iraq war and its dire outcomes have sown reservations about another chemical weapons-based campaign with even greater potential for catastrophe and international conflagration.

''The West has no appetite or intention for trying to determine the future of Syria according to its own preferences, because it has learnt from Iraq and Afghanistan that things never go to plan,'' says Rosemary Hollis, professor of Middle East policy studies at London's City University. Nonetheless, she says any deterrent strike on Syria undoubtedly has the potential to embroil regional and global players.

''By retaliating to only the chemical issue, there will of course be an effect on the dynamics in Syria, which has implications for the external powers,'' she says. ''It is one thing if it can be contained, but if it looks likely to drag down Lebanon, entangle Iraq, destabilise Jordan, threaten Turkey and derail nuclear talks with Iran, it becomes a bit redundant to argue that the conflict has nothing to do with us in the West.''

Beyond the geopolitical risks, many have pointed to the more pressing question of whether military action would in fact improve the security of those inside Syria. Not least among the unknown perils of intervention is that posed by Assad, whose ruthlessness has thus far exceeded the worst expectations of Western governments.

Syria is by now riddled with geographic and ethnic fissures from which there looks to be little way back. Atrocities by all warring factions have been documented, with groups such as Human Rights Watch warning of the ''horrifying sectarian violence'' starting to engulf the country. The opposition military alliance, the Free Syrian Army, is ideologically and strategically disaggregated. So too, some estimates suggest that as many as 1200 different rebel military units now operate on the ground, including the jihadist front Jabhat Nusra and several al-Qaeda affiliates. The political opposition abroad has repeatedly failed on co-ordination and diplomacy, and with questionable support among Syrians inside the country, it is in no position to assume leadership in the event of Assad's fall.

In light of this, leading voices have argued that the best prospects for security lie in diplomacy. Among them, the UN-Arab League envoy to Syria, Lakhdar Brahimi, has claimed there is no military solution to the crisis and called on all parties inside Syria and internationally to ''work harder together'' towards a political solution.

''For the first time Assad knows this is serious,'' says Ghias Aljundi, a journalist and human rights activist who was himself a victim of the Assad regime before fleeing Syria in the 1980s.

Like other opposition leaders, Aljundi says Syrians are now overwhelmingly, if reluctantly, in favour of intervention. ''Everyone knows that there is no way out without Western involvement - the only way to go forward is to get rid of [the] regime. Of course there will be chaos and bloodshed, but we have already lost more than 100,000 under Assad, so how much worse can we expect?''