“This was something we never expected,†he said somberly
This action was planned since February. We are under an obligation to no one to announce our military plans according to their timetable and satisfaction.
The withdrawal of the American infantry from Syria was prepared long ago and came as a surprise only to the uninformed. Trump ordered the development of a plan for leaving Syria as early as February of this year, and in April, this plan was partially declassified and made public.
https://www.americanthinker.com/articles/2018/12/are_there_any_good_guys_left_in_syria.html