The Imperial Guard is easily the largest fighting force of the Imperium. It is comprised of trillions of soldiers from thousands of different regiments, supported by a dazzling array of light and heavily armoured vehicles. They are usually the first Imperial fighting force to respond to any major invasion or uprising if the planet's Planetary Defense Force fails to suppress it. They also hold major locations of interest to the Imperium and are more often found in defensive roles than offensive.
The Imperial Guard are much more widespread than the Space Marines. Imperial Guard are also much more expendable; the loss of a hundred Imperial Guardsmen would still not equal the loss of one Space Marine. The Primarch of the Imperial Fists Space Marine chapter, Rogal Dorn, once famously quoted: "Give me 100 Space Marines or, failing that, give me 1000 other troops." (In actual game terms, however, because of a need for balance, Imperial Guard are able to fight Space Marine armies with a reasonable chance of victory.)
Imperial Guard, while weak individually, rely on infantry numbers and the assistance of powerful tanks, such as the Leman Russ Battle tank, Basilisk mobile artillery, and Chimera APC, to win. Even a small Imperial Guard division is likely to have a full complement of armored fighting vehicles. Imperial Guard, while not as bad as Tau, are notorious for poor close-combat abilities.
The Imperial Guard also have a number of specialists at their disposal such as Stormtroopers, the elite of the Schola Progenium, who have been issued better weapons and stronger armor.
Though general-purpose Imperial Guardsmen are weak in close combat, with the help of specialists such as Ogryns (brute-like Ogre creatures), their strength at close quarters is boosted. Also, some named Imperial Guard regiments have special rules like Ambush to help stun the enemy for a head start in the fighting. Regiments also have the options to take doctrines, specializing their force in some ways to make it stand out from the rest. These can include better armour for the army, or allowing them to drop into the middle of a battlefield at any time during a fight. This system makes the Imperial Guard list quite flexible.
Imperial Guard Equipment and Weaponry has a wide range from standard Lasguns to Earthshaker cannons.