It saved my brothers ass a few times in 'Nam. At that time it was called "Puff the Magic Dragon"
"The Douglas AC-47 Spooky was the first in a series of gunships developed by the United States Air Force during the Vietnam War. It was felt that more firepower than could be provided by light and medium attack aircraft was needed in some situations when ground forces called for close air support."
They are indeed vulnerable to shoulder fired missiles etc, however, they were not designed for fighting conventional wars and they only operate at night. We lost one in the first Gulf War because they stayed on target too long and the sun came up giving the Iraqui gunners a target.