Alpha Legion forces in the Stygian wars often employed attack bikes in a unique fashion that enabled them to achieve a significant tactical flexibility when employed. These unique differences between Alpha legion employment and traditional astartes codex approved deployment soon garnered the labeling of such tactics and forces as Dragoon.
Throughout the Stygian Wars Dragoons were transported via the air prior deployment into Imperial Rear areas or along the leading edge of the frontlines. With their greater speed and maneuverability they would then frequently conduct hit and run raids on Imperial armored forces. Striking suddenly destroying a few vehicles and killing a few Imperial guardsmen before withdrawing rapidly and before imperial forces could fully react.
They would then conduct such hit and run attacks on Imperial Guard bases and barracks striking quickly inflicting as much damage and terror as possible before withdrawing before retribution could be brought to bear.
These hit and run raids would also target strategic Imperial installations such as refineries or promethium drills in an attempt to disrupt them and force more Imperial forces be diverted from the frontline to garrison duty.
These raids would sometimes allow enough time for an Imperial pursuit force to be formed to stop their depredations though all too often it was a case of the Alpha Legion leading the response force into an ambush.
While these tactics were common to white scar or even raven guard units it was the additional steps that the Alpha legion attack bikes undertook that made them into a unique menace.