1.21 added several features and fixes related to combat

• Mace
• Mace enchantments
• Wind breeze
• New wind charged potion effect
• Fire aspect doesn't work when blocked with a shield
• Sweeping now applies fire aspect to all mobs
• Sweeping now applies thorns to all mobs
• Sweeping now applies the right type of damage when combined with mob type specific enchantments (e.g. smite)
• Burn time of fire protection now stacks when multiple armor pieces are equipped
• Knockback reduction of blast protection now stacks in the same way
• Use safe fall distance attribute (increases with jump boost)
• Use entity hit range attribute

And most importantly

• Support for new 1.21 enchantment effects specified in json files (there really is no other way in order to keep up with future updates..)