It does not take much political imagination to get to the point where the situation in Syria, particularly the battle for Aleppo, should invoke the principle of the Responsibility to Protect (R2P). When a government turns on its own people -- in this case, largely civilians -- it has lost the right to rule, and foreign intervention becomes a legitimate alternative.
It could be argued that R2P has been the legitimate alternative in the case in Syria for some years. However, R2P requires UN Security Council (UNSC) authorisation, which in turn requires its permanent five (P5) members not to veto such a move.
With P5 members Russia and the US using Syria as a proxy battlefield, UNSC authorisation of an international force to settle the situation in Syria has never been a realistic option.
[Tenuous ceasefire brings passing relief to war-ravaged Syria]
To the extent that the US has intervened in the Syrian conflict, it has been limited to air strikes against Islamic State and Jabhat Fateh al-Sham (formerly Jabhat al-Nusra) and in materiel support for non-jihadi anti-Assad forces. Russia, on the other hand, has directly targeted the full range of anti-Assad groups, in particular non-jihadi groups, reasonably assessing that it can leave the US to do that.
Given heightened expression of US concern over the bombing of Aleppo and, in particular, civilian areas including hospitals, Russia has replied by claiming these comments are a precursor to NATO intervention. Russia’s intention is to raise the spectre of the UNSC-approved NATO intervention in Libya, which led to the downfall of dictator Muammar Gaddafi and subsequent political turmoil in that country.
While there is no sense, at this stage, that NATO is likely to unilaterally intervene in Syria, there has been debate within the US administration about escalating US involvement under the rubric of UN Charter chapter VII, article 51 regarding "collective self-defence". Late last week, a leaked audio revealed US Secretary of State John Kerry saying he and others had lost a debate within the Obama administration for greater intervention.
Kerry did acknowledge, however, there were no legal grounds for direct US intervention against Syria’s Assad regime. Meanwhile, Russian Foreign Minister Sergei Lavrov warned of "tectonic" changes in both Syria and the region should there be such an intervention.
The US is unlikely to engage in direct intervention, at least for several months, for three reasons. The first reason is that such a war would likely be "unwinnable" in any conventional sense and could bring the US and Russia into dangerously direct conflict.
The second reason is because, in retaliation, Russia, Syria and their Iranian and Hezbollah allies could easily spread the regional conflict beyond Syria’s borders, including to Iraq, Jordan and Lebanon (but probably not Israel).
The third reason that unilateral US intervention is unlikely any time soon is because Obama came to office promising to reduce, not escalate, conflict. He does not want to leave an unwinnable war as his legacy.
However, should Hillary Clinton win November’s US presidential election and the Syrian war is not de-escalating by the time she takes office in January, it is possible that, on past form, she may consider such an intervention. But Hillary Clinton would , like Obama, be wary about a direct conflict with Russia. Donald Trump is wildly less predictable but, as voting intentions solidify, he also seems less likely to pull together sufficient swing states to achieve office.
As from the outset in this deadly game, it therefore appears that Russia continues to hold Syria’s trump cards (no pun intended).