A long list of Republicans — including several top allies of President Donald Trump — lined up in vehement opposition Monday to the president’s decision to withdraw U.S. forces from the northern border of Syria and allow a Turkish operation there.

The announcement marked a major blow to the Kurdish-led Syrian Democratic Forces, or SDF, which the U.S. relied upon heavily as the most effective fighting force against the Islamic State militant group in Syria — and prompted outrage among GOP lawmakers.

Read the rest of the story at NBC News.