He could be referring to our withdrawal from Iraq as "ceding power to Iran" which would be correct insofar as the Shia southeast is concerned. It did destabilize Iraq and drive the Sunni tribes of Iraq including even formerly secular Baathist elements of the Iraqi army under the umbrella of ISIS.
So it depends upon how one interprets what Walker said as to how informed one might conclude he is.
This is a good position to take.
We *previously* surrounded Iran.