Abstract: The 120 mm mortar concept is going through major changes. What used to be a simple indirect fire weapon for the support of infantry units is nowadays something much more. Already when simply mounted on a chassis the mortar opens up new possibilities, which the armies around the world are just starting to realise. When the concept is further developed the possibilities are even greater. This paper describes the AMOS (Advanced MOrtar System) developed by the joint-venture company Patria Hagglunds Oy. AMOS is a twin-barrelled, breech-loaded, mortar turret suitable for integration to medium-sized (10-25 ton) wheeled or tracked armoured vehicles. The two-man turret has armament comprising two independent 120-mm smoothbore mortars mounted into a common cradle with an equilibrator and a loading device. The mortars fire conventional 120-mm, smoothbore, fin- stabilised ammunition. Special ammunition, such as cargo and guided ammunition, can directly be used as these were originally developed for smoothbore barrels. The mobility and protection of the APC chassis supports vehicle survivability in the modern battlefield. AMOS is characterised by its extremely high rate of fire that gives high impact on target-the maximum rate of fire is up to 26 rounds/min and the number of rounds in MRSI (multiple rounds simultaneous impact) is as high as 14. The lethality is therefore higher than with any other mortar systems.