At the centre of every armed conflict of the 20th Century, the machine gun has been a tool of conquest - and of liberation. Everywhere, it has unleashed consequences its creators never imaged. And it was invented 140 years ago. With the help of the machine gun, Britain builds an Empire; Russia takes the Caucasus, Siberia and central Asia. The United States uses it to seize Cuba from Spain and to conquer the Philippines. Britain takes North India, Burma and Tibet. Wherever it goes the machine gun ends all resistance to colonial expansion and all the time it evolves into a more deadly machine than before. Al Capone buys three of the new "Tommy" guns in a hardware store, gets in his car, drives by a bar and blasts away at his competitors. The Chicago police decide the only way to deal with the new threat is to beat the gangsters at their own game and in 1926, the Tommy is issued to the Chicago police department. In Vietnam, the gun that helped build the empires of the nineteenth century is now mounted on aircraft. The planes circle Vietnamese villages, tilting their wings down to the left and open fire with their three side-mounted Gatlings, each firing up to 5,800 rounds per minute, five times faster than the fastest single-barrel machine guns. A new machine gun, know as Metal Storm, shoots one million rounds a minute. In one version of the gun, it has 36 barrels, each holding fifteen bullets. The gun has no moving parts but is fired electronically. As the charge fires the revolutionary new bullet expands, blocking the barrel, to stop a chain reaction. The distance between each bullet leaving a normal machine gun is about 100 feet. In Metal Storm the distance between bullets is four inches. The gun will stop missiles and tanks as easily as it stops approaching soldiers. Metal Storm will soon be available in hand-held versions. Both the pistol and the machine gun models will require little more power than the battery from a digital calculator.