The answer is a smoke curtain.
It is a dense, vertical development of smoke. It is positioned between friendly
and enemy positions to avert or damage enemy ground observation of friendly
positions. Since the smoke curtain is not placed directly on friendly troops,
it will not hinder friendly operations. Also, it activates in the event
of a fire, on condition that a means of diverting smoke away from a preferred
location or protecting an area from direct smoke infiltration.
