The formal definition of large-calibre artillery used by the United Nations Register of Conventional Arms (UNROCA) is "guns, howitzers, artillery pieces, combining the characteristics of a gun, howitzer, mortar, or multiple-launch rocket system, capable of engaging surface targets by delivering primarily indirect fire, with a calibre of 75 millimetres and above". This definition, shared by the Arms Trade Treaty and the Treaty on Conventional Armed Forces in Europe, is derived from a definition in United Nations General Assembly Resolution 46/36L, which set a threshold of 100mm. Several grammatical changes were made to that latter in 1992 and the threshold was lowered in 2003 to yield the current definition, as endorsed by UN General Assembly Resolution 58/54. Historically, large-calibre weapons have included bombards and siege guns. Late Middle Ages In the context of late medieval siege warfare the term superguns applies to stone-firing bombards with a ball diameter of more than 50 cm. These superguns were either manufactured by forging together longitudinal iron bars, held in place by iron rings, or cast in bronze with techniques generally similar to bell-founding. Known examples include the Pumhart von Steyr, Dulle Griet and Mons Meg (all iron) as well as the cast-bronze Faule Mette, Faule Grete and Dardanelles Gun. At the beginning of the development of superguns was the desire to increase the effect of the projectiles. To this end, master gunners first simply used larger powder loads. These, however, exerted larger pressure on the existing cannon and could make it burst, causing the death of the irreplaceable gunner with his crew (and even kings). In addition, it was observed that, due to their higher velocity, stone balls were shattered by the impact on the walls rather than smashing them. Thus, the mass of the cannon balls and, consequently, of the ordnance too continually increased, finally culminating in giant cannon like the Pumhart von Steyr which fired a 690 kg ball. Apart from the anticipated improvement in penetrating power, other factors such as prestige and a potential deterrent effect also played an important role. For all their manufacturing quality the superguns were only moderately successful. Their military effectiveness turned out to be out of all proportion to their overwhelming logistical demands and financial costs. For the cost of a single supergun, two or three large bombards with a reasonably smaller caliber (in German Hauptbüchse) could be produced whose firepower was enough to shatter any