A mix of Crossbowmen and Pikemen . The Crossbows deal the damage, and the Pikemen act as a "meat shield" to block the stairs.
In Stronghold Crusader, each unit has its own set of stats that determine its performance on the battlefield. These stats include: stronghold crusader unit stats
These units cost only gold, requiring no weapons or peasants. Arabian Archer (75 Gold): A mix of Crossbowmen and Pikemen
The story of every siege is not about killing his army. It’s about bypassing his 500 HP by using assassins (bypass HP with instant kill) or trebuchets (200 damage per hit). The unit stats exist only to protect that 500-HP vegetable on the throne. stronghold crusader unit stats