Back in middle ages who defended the castle from the walls and watchtowers

they were already unreachable but archers helped too

Explanation:

In order to prevent an enemy getting over the wall the castle builders selected their site with great care so that the terrain would be difficult for a belfry to cross. They then made it more difficult by digging a ditch or moat around the curtain walls in order to prevent the towers getting close to the battlements. yet archers played a great role in middle ages by defended castles and kingdoms from top while infantry troops fought.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.