The B-type Assault Droid commonly called the B-4 Super Battle Droid was a joint project between the Mustafarian Merchant Alliance and the Free Echani Alliance after the Battle of Endor. The droid was based on the design of the B-1 Battle Droid from before and during the clone wars, and the B3 Battle droid. Combining the strengths of both designs, the B1's framework and the B3's weaponry, with a more intelligent droid brain, and hardened armor.