He might be referring to soldiers dispatched in multiple operations, though.
The US' decision to pull out is major news, considering recent developments. Turkey is about to begin an invasion of SDF-held Northern Syrian territories, what this means is that the US will not be defending SDF forces against Turkey, though they did provide vast amounts of arms to the SDF prior to the decision and Trump did warn Turkey tweeting "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". Russia also appears to have given green light to the Turkish operation. Assad's regime is silent on the issue, though it's hard to imagine Russia green lighting the operation if Assad were to be opposed to it. He did declare SDF forces as a threat to Syria's territorial integrity last month.
Inevitable, really. The US set the stage for an all-out war between Turkish Armed Forces and Syrian Democratic Forces by refusing to see what they were doing for what it is and simply trying to buy time. The entities that form the SDF have direct ties to the PKK, the Kurdish separatist group that has been engaged in a conflict with Turkey for 40+ years and has carried out a countless number of attacks on civilians and public institutions. Using, among the local forces in the region, only the SDF to battle ISIS, allowing them to retain control of vast areas that previously were not in their control and ethnically cleanse Turkmen and Arab populations from said areas was always going to initiate a military response from Turkey. The US continued to ignore it, tried to buy time, and in the process not only initiated another conflict, but also pushed Turkey further towards Russian influence.
This is how many times the US have completely bottled its intervention-based strategic pursuits and helped create/exacerbate complicated problems in the region?