Daraa: Assad's violence, western indifference; a painfully familiar story

The attack features favoured tactics of the regime and its allies. It began with shelling. The offensive notably includes massive aerial attacks by the Syrian and Russian air forces, of the sort the war has previously brought.

Monitors accuse the regime and its allies of deliberately targeting health centres in the country's south - hardly a novel claim. Aircraft aligned with the regime coalition struck numerous similar sites in previous offensives.

All this is familiar. The results of such tactics have been demonstrated on battlefields across the country.

Observers know, by now, that this is how the regime wages its war. Its strategy requires wearing down rebel-held areas, surrounding and isolating them, and finally liquidating those pockets that remain.

At the liquidation stage, these battles are at their most violent. Regime and allied forces, deep into territory which had, until recently, been held by others and whose inhabitants hold different loyalties, show no restraint.

They are hardly amenable to local sympathies. This is when massacres happen, like those reported in Aleppo during its capture in 2016.

It is at this stage - perhaps to spare pro-Assad forces the problem of entering urban areas keenly defended and bristling with local hostility - that the regime has been known to use chemical means to gain advantage, either to soften up defenders, or to terrify them and the civilians they live among into surrender.

That is the likely rationale behind the regime's chlorine attack on Douma in April.

Chemical weapons and massacres: Both are tactics of collective punishment, employed consciously to dissuade further resistance.

Tactics are replicated and repeated with barely a whisper of dissent

Because all this is known, it is depressing – though not all that surprising – that the United States recently told Daraa's defenders that they are on their own.

This calcified a broad and long-standing truth, one which applies to others as well as the United States. The truth is that the United States and the western powers have effectively given up on Syria's armed opposition. They will go unsupported. Not a finger will be lifted in their defence.

American frankness means that at least now Daraa's defenders know where they stand, and what their former friends truly think of them.

It represents a direct abandonment on the part of the Americans of those forces to which they had previously been allied.

The consequences of that abandonment, like the content of the regime advance, are known. They are vital to explicate fully, and to understand.

If Daraa is allowed to fall to the regime, the continued advance of the regime coalition, absent external checks, is effectively guaranteed.

Assad has the support of two external states - Russia and Iran - as well as a region-spanning network of militias and proxies. All these are converging to attack Daraa.

The United States and the western powers have effectively given up on Syria's armed opposition

Those present in Daraa, the defenders of the town where the Syrian revolution began, have only themselves.

Abandoning those rebels has obvious consequences. It seals the deaths of civilians and combatants, and effectively wills the regime to dominate new territory.

Such things happen in war.

Read more: Syrian rebels agree to surrender more Daraa towns to regime

But there is more going on. Russian and Iranian-linked forces have recently tussled. They are not a united front. Russia is, absurdly, in the process of being petitioned by Israel and others to evict Iranian forces from Syria's south.

The reasons behind this are clear. Israel is wary of any Iranian encroachment of its border. And any conquest of Daraa would effectively allow Iranian-linked proxy forces - which are thoroughly integrated with regime military structures - to move closer to the border with Israel.

This comes at a time where open conflict between Israel and Hizballah, and even between Israel and Iran, seems more and more likely.

Responding to war crimes past does little to comfort victims of war crimes present

Israel's apparent unwillingness to help Daraa's defenders has met with justifiable criticism, both because it is insensible and because defending Daraa would constitute doing "the right thing".

That last point is essential. Aside from these geopolitical considerations, there is the matter of moral responsibility.

The United States, Britain and France recently undertook action to deter the chemical crimes of the Assad regime. That policy required the allies' acknowledgement of how the regime wages war, and the extent of degradation it is prepared to reach.

All three nations are also pledged to the upholding of 'de-escalation zones', the nominally semi-safe havens, one of which is Daraa.

	The Russian-Syrian assault on towns in the Daraa countryside has led over 150,000 to flee to the plains near Jordan [Anadolu]

That the system of de-escalation zones was farcically conceived and never fully implemented does not justify moral absentmindedness. It does not invalidate promises made; it does not allow for looking away.

To enable the regime not only to breach this de-escalation zone, and in so doing to allow it to commit crimes, is plainly wrong. It is an unadorned and inarguable rejection of responsibility.

Worse still, the result of the American message and the inertia of NATO nations serves actively to repudiate those rebels whom the West supported - at least rhetorically - not so long ago.

It also undoes any good April's action could claim to have done. Responding to war crimes past does little to comfort victims of war crimes present, or war crimes to come.

Pleading ignorance of the regime's modus operandi is one thing; but consciously confronting its worst elements only when such action is convenient, invalidates such a defence.

All this speaks ill of British, French and American foreign policy and indeed the political morality of those nations, as the same stories of violence play out in more of Syria.

Tactics are replicated and repeated with barely a whisper of dissent, nor the possibility of anything which might cause this new attack to diverge from what is known and what is expected.

We have seen this happen before. We know now what abandoning Daraa will mean.