Turkey’s invasion of eastern Syria last month using extremist Syrian rebel groups against the Kurds was “intentioned-laced ethnic cleansing” and “a war crime, when proven,” said a senior US diplomat in a strongly worded internal memo.The memo, by William Roebuck, the deputy special envoy to the Global Coalition to Defeat ISIS and a senior adviser to the special representative for Syria engagement, was published in full by The New York Times on Thursday. Roebuck was one of the lone diplomats on the ground in the last weeks and over the last year as the US diplomatic footprint shrank.He worked closely with the US-backed Syrian Democratic Forces, the Kurdish-led forces that defeated ISIS in eastern Syria and were supporting the US and international community. But then on October 6, the US withdrew from part of northern Syria and Turkey attacked the SDF.The US did almost nothing to help its former Kurdish allies, enabling at least 100,000 of them to be ethnically cleansed and hundreds to be killed. The excuse was that the attacking force was America’s NATO ally, Turkey, and the US couldn’t stop it. But hundreds of SDF members, some trained and armed by the US, were killed.The US has now admitted that in fact, it was ill-disciplined members of the former Free Syrian Army, many of them Islamists and extremists, who attacked the SDF. The US monitored the attacks and cleansing of civilians and war crimes and did nothing. Eventually Washington pushed for a ceasefire on October 17. But it was too late for Hevrin Khalaf, a female political party leader pushing for peace. She was dragged by her hair by Turkish-backed militants and executed.Now the real US view among some diplomats is emerging. The State Department knows about Turkey’s backing of “ill-disciplined Arab militias” and monitored their attacks on civilians and the videos of their war crimes.But US diplomats are split on what to do. James Jeffrey, who is the anti-ISIS envoy and Syria engagement czar at the State Department, is more pro-Ankara.He wants to speak softly about Turkish-backed attacks. But others, in Congress and elsewhere, feel the US betrayed allies and has looked weak in the face of threats.Roebuck’s memo is the harshest so far. “The US government should be much more forceful in calling Turkey out for this behavior,” the memo says.Instead, the US invited the Turkish leader to Washington and sent a major delegation to Turkey this weekend. The memo says that the SDF lost 10,000 fighters defeating ISIS and has 20,000 wounded.“We asked these people to take on this fight,” Roebuck writes. “We asked them to fight for us, for the international community, to put almost exclusively on their shoulders this burden.”So the US helped create the SDF and train 100,000 of its members. Some diplomats called this a “transactional” approach. But the US wasn’t just doing a transaction. It made the SDF dependent and asked the SDF not to work with the Syrian regime, Russia or others. It isolated the SDF and excluded it from Geneva peace talks. Then on October 9, the US opened the airspace so the SDF could be bombed and killed. Civilians were forced to flee. Roebuck says that is “intentional-laced ethnic cleansing.”He says the SDF worked to do what the Americans asked. It worked with Sunni tribes. It removed forts when Turkey demanded it. It took cities and lost men and women fighting. But when Turkey said the SDF was a “security concern” and claimed it was linked to the PKK, US officials didn’t bother to investigate if there were any security threats.US diplomats knew Turkey was being misleading and that the threat was “perceived,” but not real. “The border stayed quiet on the Syrian side the entire time, over 20 months.”There was no threat, but Turkey used this as an excuse to attack. Turkey had impunity as a member of NATO, a “NATO get out of jail free card,” the US official says. Other countries did nothing to stop Turkey or its extremist allies it unleashed on October 9. Instead, the international community “sputtered.”The US didn’t guarantee the SDF it would stop an invasion but in January 2018 the US made sure the SDF didn’t reach out to the regime to stop a similar Turkish invasion of Afrin. “Turkey and its jihadi mercenaries attacked last year, dispossessing 170,000 people,” Roebuck notes. The US told the SDF that as another Afrin would not be happen in eastern Syria. Then on October 9 the US allowed another ethnic cleansing like in Afrin in the exact same format.The US lied to the SDF and misled them. The US diplomat writes that Washington’s guidance after Afrin was to reassure the SDF. “We are your close partner, Afrin can’t happen here,” they told the SDF. They were wrong. More than 400 SDF members died, civilians were burned and died, children were killed in bombing, and Washington did little to prevent it, according to the recent revelations.Now the SDF may be living on “borrowed time.” The US knows that Turkey spearheaded its operation with “armed Islamist groups on its payroll.” Some of the groups were formerly allied with ISIS and Al-Qaeda according to the memo. Roebuck urges holding Turkey responsible for the ethnic cleansing that has taken place and the threat to minorities and Christian communities. The US should make it clear that the people who fled “must be able to safely return.” In addition, the memo argues that “we should insist Turkey bear all the diplomatic and reputational costs for their venture and seek to prevent President [Recep Tayyip] Erdogan from flooding this depopulated zone with Syrian Arab refugees.”The tough language from the memo, and the US State Department briefing on November 6, shows that the US was aware of crimes committed from the first days of October 9 and that Turkey was using Syrian rebel extremists to attack the SDF.It reveals the US did nothing to help refugees or displaced people and shows how the US helped isolate and mislead the SDF, giving it few tools to do anything and making sure it was disarmed diplomatically from opposing the attack on October 9.One could almost conclude that the US helped create the SDF just so it could undermine and destroy it later when it was no longer a useful tool against ISIS. This cynical policy has left some Americans ashamed and feeling that they betrayed key friends and allies and bolstered extremism.