A Special Forces team chief uses violet smoke to signal an Mi-17 helicopter to land to extract Coalition Forces from Gulistan district, Farah province, Afghanistan, April 12, 2009. The team uses smoke to communicate with pilots when executing an extraction from certain areas.
(U.S. Army photo by Spc. Joseph A. Wilson/Released)

A Special Forces team chief uses violet smoke to signal an Mi-17 helicopter to land to extract Coalition Forces from Gulistan district, Farah province, Afghanistan, April 12, 2009. The team uses smoke to communicate with pilots when executing an extraction from certain areas.

(U.S. Army photo by Spc. Joseph A. Wilson/Released)