During the late Late Medieval Period, which began in 1400, the Culverin was the most fearsome siege weapon available. It used light cannonballs, and they did not explode, but the range and speed with which it fired made it a formidable weapon. It was the primary weapon used for besieging a fortress, and any other castle, by this stage and was quite useful for piercing thick platemail and reducing morale of enemy troops.

The culverin was the latest evolution in a line of cannons beginning with the serpentine, then the demi-culverin and finally the culverin. It was a smallish cannon mounted on large wheels with a very long and small barrel. It had a low angle of fire, and was more or less the gunpowder adaptation of the ballista. It could be aimed straight, and was very accurate, comparitively. The cannonballs were small and did not explode, but the speed at which they were launched caused a high impact that could pierce armour and crack castle walls.

It was the first weapon that could actually be called artillery as we know it today. In fact, it looked almost like a very archaic howitzer, and in effect, it was used far more as a howitzer would have been than how a ballista would have been. While it could be pointed straight and used to pierce armour, the target still needed to be in relatively close quarters, otherwise the cannonball would drop over time. Therefore, it was far more often used as a demoralizing and harrassment weapon by bombarding enemy with cannonballs, much as artillery had been used.

When it came to sieges, however, it reverted back to your standard "break down the wall" siege weapon. It was incredibly effective against castles, moderately effective against citadels, and the only real effective attack against a fortress. It was quickly obsoleted by the renaissance, however.