Trump’s surprise decision on Wednesday to completely withdraw US troops from the country triggered criticism from some Republicans and concern from America’s allies.

The announcement of a withdrawal of troops on the ground had not necessarily meant an end to the air war since, unlike ground troops, major US air assets are not based in Syria and instead fly into the country from nearby nations. The US air operations center for the air war is located in Qatar.

US officials told Reuters that the timing of the end of the air campaign would be linked to the withdrawal of the US forces but declined to set a date for when that would happen.

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