Donald Trump has just signaled a dramatic shift in US policy in northern Syria, betraying his erstwhile allies the Syrian Democratic Forces (SDF), in which the Kurdish YPG militia are the dominant force. The 60,000 SDF fighters had provided him – and Obama before him – with the boots on the ground that defeated the ISIS ‘caliphate’. The SDF have said they will defend north-west Syria “at all costs”: those costs are likely to be very high.

However, only the unwariest will be surprised that US imperialism brutally casts aside its allies the minute they are of no further use to them. After a late-night phone call between the US president and Turkish strongman, Recep Tayyip Erdoğan, the White House issued a cryptic statement:

“Turkey will soon be moving forward with its long-planned operation into Northern Syria. The United States Armed Forces will not support or be involved in the operation, and United States forces, having defeated the ISIS territorial ‘Caliphate,’ will no longer be in the immediate area.”

With breathtaking cynicism Trump posed as an antiwar politician, tweeting he was “getting out of these ridiculous endless wars” and that “Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds will now have to figure the situation out.”

Immediately US forces began withdrawing 1,000 troops from positions along the Turkish-Syrian border. A Turkish onslaught could begin at any time. Their declared objective is to occupy a long strip of Syrian territory.

Republicans on Capitol Hill like Senator Lindsey Graham, plus the US security establishment and armed forces, are plainly dismayed by Trump’s precipitate capitulation to the Turkish president.

However, Pentagon spokesman Jonathan Hoffman has said “the Department of Defense made clear to Turkey – as did the president – that we do not endorse a Turkish operation in Northern Syria”. Not endorse but, of course, not oppose either. In fact, it is likely that Turkey’s plans will have been cleared with Trump.

Still, to cover himself, Trump issued the frankly unhinged threat: “If Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey (I’ve done before!).”

Turkey has actually produced a map showing a “safe zone” some 300 miles long and 18 miles wide into which it plans to drive two million of its 3.6 million Syrian refugees. This would produce something like the Israelis have created in Gaza. The zone would be just about as safe too, for its unwilling occupants, since attacks on “terrorists” from the air will certainly continue.

One major worry for the US and the EU is the thousands of Islamic State prisoners in SDF-run detention camps. The SDF have said that if and when they are forced to defend themselves they would withdraw guards from the camps and recently liberated areas, which contain some 20,000 foreign nationals that their home countries, especially in Europe and North America, are refusing to take responsibility for.

Though the blood-soaked Syrian dictator Bashar al-Assad has denounced any invasion of Syrian territory as a violation of his country’s sovereignty, his Russian allies have indicated benign toleration of Turkey’s occupation plans.

Doubtless the SDF fighters will soon be caught between the hammer and the anvil of the Turks and the Russo-Syrian forces. War in these conditions will be a horrific bloodbath not only for the grotesquely outnumbered SDF fighters but for the huge numbers of refugees. Additionally, if western Kurdish parts of Syria are occupied, Assad, Putin and even Erdoğan will be emboldened to move against the statelet of Rojava too. This would conclude the brutal endgame of the Syrian Revolution and civil war.

This outcome shows the murderous folly of relying on or becoming proxies for either of the rival imperialist blocs. Likewise, the ambitious regional powers, Turkey, Iran and Saudi Arabia, have also used, and cruelly abused for their own nefarious objectives, forces that were seeking to liberate their peoples.

The dilemma they face is that there are few organised forces worldwide who could come to their aid in materially significant terms. Syrian and Syrian Kurdish forces certainly deserve the support of socialists and anti-imperialists worldwide in their resistance to the rival butchers Erdogan and Assad, as well as the war criminals in the White House and the Kremlin.

Socialists must demonstrate worldwide against a Turkish invasion and where possible organised workers should impose sanctions on ships, trade and communications to signal their solidarity. In addition, solidarity with refugees from the region must be seriously stepped up. We demand that Europe and Britain open its borders and provide safe passage, housing and work for all victims of its bloody colonial adventures.