The Imperial Guard is the largest fighting force of the Imperium of Man. It is comprised of countless billions of men and women -- hundreds of thousands of different regiments, supported by a vast array of light and heavy armoured vehicles that provide the Guard's primary offensive punch. They are usually the first Imperial force to respond to a threat if a planet's Planetary Defence Force (PDF) fails to suppress it. They also garrison major locations of strategic or cultural interest to the Imperium and are often found in defensive roles. The Imperial Guard is often referred to as the "Sledgehammer of the Emperor"; the sheer amount of force that the Imperial Guard can bring to bear on the enemy is devastating, but is not as direct or as precise as their Space Marine allies, who are described as the "Scalpel of the Emperor."