WASHINGTON – Two days before President Trump announced that he would pull U.S. military back from the border zone in Syria, Americans and their Kurdish allies had removed senior ISIS fighters from the battlefield, according to a U.S. official who was not authorized to speak publicly.

The capture of the two fighters occurred as part of daily regular commando raids U.S. forces had been running with Kurdish soldiers, the official said.

Trump's abandonment of Kurdish allies fighting ISIS has shocked members of the U.S. military and left it scrambling to protect American forces in Syria – and to look on as those they worked with side by side only a few days ago are now under attack as Turkey's military continues to step up assaults on the region.

Thursday marked the second day of Turkey's assault on Kurdish forces in the region. Turkey launched the assault because it views a Kurdish militia that dominates the U.S.-backed Syrian Democratic Forces, or SDF, as a terrorist group.

Earlier this week, Trump said he was delivering on a campaign promise to remove U.S. troops from "ridiculous endless wars." Trump also defended his decision on Wednesday to end U.S. support for the Kurds, saying they had failed to fight with Americans in World War II.

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The Pentagon has issued few statements since Trump's decision, blaming Turkey for acting unilaterally and calling for a "safe zone" to be established in northeastern Syria.

'None of our allies can trust us'

The Kurds formed the backbone of the counter-ISIS ground force, backed by the U.S.-led air war, that has retaken virtually all the land seized by Islamic State fighters since 2014. The Kurds have lost 11,000 troops in the fighting and have seen another 20,000 wounded. Their bloodshed and support has led to a kinship understood by many U.S. troops who view the U.S. withdrawal of support as a betrayal of a dedicated ally, the official said.

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"None of our allies can trust us anymore," Sen. Richard Blumenthal, the Connecticut Democrat and member of the Armed Services Committee, said in an interview. "The biggest loss here apart from the slaughter of innocent and loyal fighters on our side is the shattering of trust. The loss of our word as a bond. No one can rely on the United States if we abandon our fiercest most loyal allies who have literally shed blood for us."

Trump's decision has led to ad hoc measures to protect U.S. troops and attempts to mitigate losses to ISIS, the official said. Among them:

A hotline established with Turkey to notify U.S. commanders of areas where bombs will be dropped to ensure American troops are out of harm's way.

The movement of 50 U.S. troops from the area contested by Turkey and the Kurds to two American outposts in Syria. Drones are being flown over the area to protect U.S. forces.

Kurds continue to guard about 30 prison camps holding about 10,000 ISIS detainees. About 2,000 of those prisoners are foreign fighters from 50 countries, from China to Canada.

U.S. forces are safe, the official said, and the 50 troops relocated to outposts represent a fraction of the 1,000 remaining in Syria.

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Deaths in Syria, but may be inflated

Turkey launched the assault because it regards a Kurdish militia within the U.S.-backed Syrian Democratic Forces, or SDF, as a terrorist group. About 30,000 Kurdish fighters and civilians have been displaced by Turkey's offensive.

Turkey is expected to turn over the fighting to local forces it backs, the official said. A second U.S. official said Turkey, a NATO ally, has been cut off from receiving U.S. intelligence on the region.

The Syrian Observatory for Human rights estimates that 16 SDF fighters have been killed and dozens wounded. Erdogan has said "109 terrorists" have been killed. The U.S. official cautioned that both sides may be exaggerating losses or gains for propaganda purposes.