From the Movies
While critics would be quick to point out a battle droid's mindlessness as a fault, the proponents of the mechanized soldiers would counter that it is instead a virtue. A mindless soldier is a loyal soldier, unquestioning of orders, easily controlled, and absolutely fearless.
It was the invasion of Naboo by the Trade Federation that showed the galaxy not only the effectiveness of battle droids, but also the glaring oversights in their design. Against a peaceful populace, the Trade Federation army of battle droids was able to quickly conquer and take control of the Naboo population centers. These droids would blindly obey orders spoken to them by their commanders or transmitted to them from an orbital Droid Control ship. The efforts of Bravo Squadron, and Anakin Skywalker in particular, destroyed the Droid Control Ship, thereby rendering the army useless.
Battle droids are tall, gaunt humanoids with exposed joints and bone-white metal finishes that gives them an eerie resemblance to animated skeletons. Battle droid infantry is frightening in its uniformity -- only a numerical marking on the back of a comlink booster pack serves to distinguish one droid from another.
Droids with specialized functions have distinct colored markings on their armor. Blue denotes pilot droids. Red denotes security droids. Yellow denotes command droids, which function with increased autonomy compared to the standard infantry.
Battle droids are very efficient. Their humanoid builds allow them to operate machinery and pilot a wide variety of war craft designed for organic pilots. For the Trade Federation, the battle droid infantry piloted STAPs, MTTs, and AATs as well as their colossal battleships. For ease of storage and transportation, battle droids could compress into less than half their size.
Following the Naboo debacle, the Galactic Republic enacted strict legislation that prohibited the use of battle droid armies. The Trade Federation has shown its disrespect for Republic law in the past, and for years, many feared that the numerous foundries scattered throughout the galaxy were still churning out assembly lines of tireless soldiers.
From the Expanded Universe
In the troubled times of the Galactic Republic's waning days, many nations and worlds once again have little choice but to resort to military hardware to preserve their interests. For a time, the existence of mechanized legions were but whispered rumors, but as the Republic continued to lose control of outlying territories, their presence became indelibly felt.
The budget-minded Trade Federation cut valuable corners in the production of their Baktoid Combat Automata battle droids. These units were rushed into production to meet the Trade Federation's sudden military needs. A mindless soldier is aninexpensive soldier, a laudable trait in the slit-pupilled eyes of the Neimoidians. The cost of thousands of individual droid brains was avoided by instead relying on a Central Control Computer (CCC) housed in a modified Trade Federation battleship.
The command and security-division droids have some level of autonomy, but all battle droids are ultimately subservient to the commands of the CCC. If a droid loses contact with the control signal, it enters a stand-by hibernating mode. If deactivated, or damaged to considerable degree, a battle droid deactivates the electromagnets holding its joints together. Though this makes the droid somewhat fragile, it does prevent the spread of damage and allows the droids to be easily salvaged for future repair and reuse.
Motion-capture data of highly trained organic soldiers gave the battle droids a flexible array of combat stances, positions and maneuvers, but the droids themselves were only as strategically capable as their programmers aboard the Droid Control Ship.
Following the fiasco at Naboo, a new generation of battle droids was developed that featured enhanced intelligence and independence. Raith Sienar was assigned a protective escort of such droids for his mission to Zonama Sekot.
Behind the Scenes
The earliest designs of the battle droid were clearly inspired by the stormtroopers of the classic trilogy, suggesting the evolution of large-scale combat in the
Star Wars galaxy. The finished droid's proportions are reminiscent of African sculpture. Early design had towering droids twice the height of humans, but subsequent iterations brought its height down to normal size.
