A squad automatic weapon (SAW), also known as a section automatic weapon or light support weapon (LSW), is a man-portable automatic firearm attached to infantry squads or sections as a source of rapid direct firepower. Weapons fulfilling this role can be light machine guns, or modified selective-fire rifles fitted with a heavier barrel, bipod and a belt/drum-fed design. Squad automatic weapons usually fire the same cartridge (though heavier-bullet variants are preferred) as the assault rifles or battle rifles carried by other members of the unit. This reduces logistical requirements by making it only necessary to supply one type of service ammunition to a unit. These weapons are light enough to be carried and operated by one infantryman, unlike medium machine guns (such as the M1919 Browning) that require a crew to operate at full effectiveness; or heavy machine guns (such as the M2 Browning or the DShK) which fire more powerful cartridges but are also crew-served and typically also require a mounting platform to be operable. Overview One of the first weapons used in this role was the Madsen machine gun. Although limited in today's terms, the Madsen was introduced in an era when the standard infantry rifle was a bolt-action repeater with fixed magazines reloaded with single rounds or chargers; sustained rapid fire with these weapons could be maintained only for very short periods of time. The Madsen was capable of fully automatic fire; despite having only limited magazine capacity, this was still more than that of the infantry rifle, and it was of the quick change detachable box magazine type. Though over 100 years old, the Madsen is still in limited use today. The standard machine guns of this era were of the Maxim type. Used by the British, Germans, and the Russians, these weapons were bulky, heavy, tripod-based, and water-cooled, they required a team of four men and, although excellent in the defence, were not suited to manoeuvre warfare. Another pioneering weapon in this role was the Browning Automatic Rifle (BAR). Introduced late in World War I, it remained in front-line service into the Vietnam War. Intended originally as an automatic rifle capable of delivering suppressing "walking fire" in the advance, the BAR came to be used in the light machine gun role. During World War II, as the importance of having a source of mobile automatic fire increased, the number of BARs in a unit also