Staffan de Mistura’s office recently stated that he will shortly stand down as the United Nations’ special envoy to Syria. This announcement impelled cordial official references to the man and his work from governments and non-governmental organizations across the globe, but occasioned little sadness.

The conflict in which de Mistura worked brought about the destruction of a nation and the deaths of half a million.

Knowing this, experiencing this, leaves little sympathy left for the departure of a single diplomat, no matter his credentials.

And those credentials, though his four decades at the United Nations and time in the Italian government seemed technically promising, included little prior knowledge of or involvement with Syria. That attitude is something which was replicated during de Mistura’s time in post.

Esteem was extended to de Mistura by journalists in part because he seemed to care. He was famed for his empathy with refugees, his father having suffered the indignities of displacement after the Second World War. De Mistura made an art of giving anguished interviews.

But this caring demeanor did not preclude de Mistura from accepting and failing to challenge the savagery of others. Despite the United Nations’ eventual attribution of chemical attacks and other war crimes to the regime of Bashar al-Assad, the regime’s self-proclaimed sovereignty was never tested, never rejected, never undermined by the UN’s special envoy. At all times, de Mistura maintained, the regime was “a part of the solution” in Syria.

The state and its complaints were not only comparable with the victims of that state; they were deserving of a special warrant of legitimacy which no violence could break. Nor did de Mistura’s own acknowledgement that the regime did not want a negotiated settlement ever change his mind.

Geneva’s hotels and conference centers were kept busy during endless rounds of negotiation, but nothing peaceable emerged from those closed rooms. This changed nothing for de Mistura. The special envoy could only conceive of a peace process involving the regime, no matter how distasteful other parties found the prospect of sitting across a negotiating table from thugs and murderers and criminals.

That distaste, indeed, was treated as ungoverned emotion; the UN-approved path the only rational response to Syria’s suffering. But when a regime whose war machine has been compared to an engine of “extermination” fails to rein in its territorial expansion, fails to stop the killing and fails, finally, to engage in any seriousness with those promising a peaceful settlement, exactly how rational, opposition activists asked, is persisting with that path?

De Mistura’s vouching for Assad’s legitimacy could only alienate those for whom the regime was not the solution but the problem, and for whom any “solution” allowing for the survival of the regime would be seen to solve nothing.

Opposition figures made their objections clear; de Mistura’s treating the regime as a legitimate partner—overestimating its investment in any peace worth having, overstating the importance of its sovereignty long after Assad became a puppet ruler of a rump state—rendered all attempts to heal Syria moot.

Pacification, the strategy of the regime and its Russian and Iranian allies, is not peace. The special envoy appeared to believe those who fought a brutal war of pacification could be turned onto peace. He was wrong.

“De Mistura should have said that the regime made his mission impossible but he didn’t and that cost Syrians blood and devastation,” Yahya al-Aridi, a spokesman for the Syrian opposition, told The National.

That this never happened is a matter of public record. So too is the list of numerous UN-brokered ceasefires which fell through, or failed to take root.

In fact, these ceasefires themselves eventually became an integral part of the regime’s strategy of surrounding, starving, and crushing pockets of opposition. Knowledge of these tactics was never allowed to interfere with the diplomats’ work, whose high-flown notions coincided perfectly with the perpetual belief that peace was still at hand; that murderers could be treated as, and take their place among, rational adults; that this time the guns could fall silent for real.

After the Russian intervention which saved Assad from overthrow, de Mistura absurdly urged Vladimir Putin, the man helping Assad to win the war, to point his client state in a more peaceable direction.

The above are terrible failures, but they are to an extent explicable. De Mistura’s two predecessors did not succeed in Syria; indeed, both Kofi Annan and Lakhdar Brahimi ended their postings in ignominy. It was always likely, therefore, that de Mistura would share that fate.

But the latter’s failures go beyond the path forged for him to follow. He made his own mistakes, and must be held accountable for them.

To end, it is instructive to survey the situation as the Syrian war approaches what could be its own conclusion. At stake is the fate of Idlib province, which was and remains likely to be overrun and destroyed by the regime and its backers when that coalition decides the moment is right.

De Mistura will see out his term before this final assault, a result he and his colleagues did much to facilitate. But one aspect relating to Idlib’s fate must not be forgotten amid the general criticism leveled at the departing envoy, an aspect found in de Mistura’s plan for the province.

That plan would have involved the creation of “humanitarian corridors” through which civilians could travel to avoid the worst of the fighting. The destination of those who travelled these corridors would have been uncertain. It is likely those purportedly rescued from violence would have ended up merely placed in camps guarded by UN peacekeepers. The precedent for such things is hardly promising.

An extra element added specific absurdity into the proposal. It included the possibility of de Mistura’s offering to go to Idlib himself to serve as a human shield if his design was not adhered to by all parties.

Syrians are lucky the offensive never took place, and luckier still that the plan was never put into operation. But the image of de Mistura in Idlib, maybe linking arms with others in pious protest at an offensive he effectively greenlit—an offensive carried out by the killers whose legitimacy and rationality he defended—is one which will live long in the memory. It serves as an apt metaphor for his time in Syria.