When Russian warplanes swooped down on a United Nations convoy trying to deliver humanitarian aid to civilians near Aleppo last week, they did not just blow to smithereens 20 innocent people and desperately needed supplies – they also demolished the already-tattered shards of United States policy in Syria.

A few days earlier, American warplanes had, in an obvious error, attacked the ground forces of Syrian president Bashar Al Assad. They apparently mistook them for ISIL or Al Qaeda terrorists. And, even though the 60 killed were combatants fighting on the side that has caused the overwhelming amount of death and suffering in the conflict – and therefore arguably merited such an attack – the Americans quickly acknowledged the error and even apologised.

The Russians, by contrast, brazenly deny their cynical and brutal atrocity, although no one believes them.

There is only one word for the American attack: mistake.

There is also only one word for the Russian attack: terrorism.

This isn’t indirect “state-sponsored” terrorism. It is direct state terrorism of a particularly vicious variety. Indeed, it is probably the most heinous act of state terrorism by a major power since the end of the Cold War.

The American response – “urging” Russia and Syria to please stop bombing and murdering civilians – was shameful. In the name of pursuing a ceasefire, and ultimately a peace agreement, in Syria, Washington has now reduced itself to serving as the unwitting dupe of the Kremlin, Mr Al Assad and their key partners, Iran and its terrorist proxy, Hizbollah.

President Barack Obama seems set to be the first two-term US president in many decades not to have suffered a manifest, obvious, major scandal in his second term. But the bizarre surrender of both American interests and values in Syria may ultimately be recalled as his latent second-term scandal.

The incoming president, in all probability Hillary Clinton, will be inheriting the most mishandled major US foreign policy since the Iraq invasion. The Obama administration has allowed the Syrian conflict to get so far beyond American influence, and ceded control so firmly to Russia and its nefarious allies, that fixing the policy meltdown has become infinitely more difficult than avoiding it ever would have been.

US policy in Syria must be urgently rescued from its present crisis. That will be difficult, but a set of clear, simple guidelines can help.

The first principle must be to start actively protecting innocent people in Syria. Russia’s state terrorism – as are daily regime attacks on civilians with weapons ranging from barrel bombs to chlorine gas – is a prime example of what can no longer be tolerated. The United States needs to start flexing its political, diplomatic and even military muscles to ensure that, in at least some places, innocents are no longer murdered with abandon and impunity.

Washington should establish, with partners or even alone, safe zones in Syria free of bombing attacks from above and the pro-Assad ISIL and Al Qaeda killers on the ground. If this means shooting down Syrian, or if necessary, Russian, warplanes, so be it.

No reasonable person could blame Washington for starting to reassert itself in the region by protecting innocent Syrians from such wanton slaughter. Many would applaud.

Second, sustained actions should be taken to alter the balance of power on the ground and disabuse the regime of the notion that it is winning and doesn’t need to compromise. For a political agreement to become viable, those around the dictatorship must understand that they must make a deal in order to survive. Otherwise they will never make any compromises.

Third, to reclaim American credibility, Washington must revive its dormant, but indispensable, former policy that Mr Al Assad – a soft-spoken but monstrous, and in today’s global scene totally unrivalled, war criminal – has no role in Syria’s future and must go.

Mainstream rebel groups urgently need substantial incentives to ally firmly with Washington and decisively turn against Al Qaeda-affiliated organisations. It’s not hard to incentivise those at war. All that’s required is the will, persistence and resources.

Finally, US policy must always reflect and communicate the core understanding that ISIL and Al Qaeda, and the Assad dictatorship, are two faces of the same sectarian total-warfare coin.

The terrorists can’t be defeated, or even successfully marginalised, if efforts to achieve that are perceived as strengthening the dictatorship. Effective Syria policies must undermine both simultaneously, or at least not strengthen either, and must be widely viewed that way.

Because change is constant and events are always moving, especially during war, it’s never too late to act. The next US president must redeem American policy in Syria.

The first step is for Washington to forcefully re-engage by using all reasonable means, including military force if necessary, to begin to end the mass slaughter of innocent Syrian civilians.

The American moral and political capitulation in Syria cannot continue. Enough is now surely enough.