It was designed to be very independent so that the mega battle droid could keep fighting if the Clone Wars ended in a Republic victory. The B4 mega battle droid began development during the Separatist Crisis, but was not finished until 20 BBY. The B4 carried multiple thermal detonators, and used them to neutralize large groups of enemies or to destroy small vehicles. The B4 was also equipped with a small missile launcher mounted on its left shoulder. The left arm was equipped with either a flamethrower or a retractable vibrosword. Similar to the B2 battle droid and B3, the mega battle droid had dual wrist blasters on its right arm, but unlike the B2 and B3, could use handheld weapons and was also very effective with them. It was often considered to be the most advanced battle droid ever made.Дespite being much smaller than the B3 ultra battle droid, it had a similar armament and just as strong yet much lighter armor. The B4 had more complex programming than any other droid in the B-series line, making it very intelligent but also causing numerous errors. The B4 mega battle droid was based on an entirely new frame that had the durability of the B3 ultra battle droid, the agility of a BX-series droid commando, and the intelligence of an ST-series super tactical droid. It was one of the most independent, powerful, and expensive battle droids in galactic history. The B4 mega battle droid also known as simply the mega battle droid, was an advanced battle droid model used by the Confederacy of Independent Systems late during the Clone Wars in limited numbers.