Rather than use flesh-and-blood warriors, the Separatists prefer mindlessly loyal soldiers that are unquestioning of orders, and easily controlled. The soulless ranks of their battle droid armies consists of tall, thin robotic soldiers with exposed joints and bone-white or rust brown metal finishes that gives them an eerie resemblance to animated skeletons. Battle droids are very efficient, and can be controlled from centralized command centers, like the enormous Droid Control Ships used by the Trade Federation. They are dim-witted, often suffering programming glitches that give them quirky personalities that are too slow to adapt to enemies like Jedi Knights and clone troopers.
At the time of their introduction, the Republic clone troopers represented the future of galactic warfare. Far superior to battle droids, the clone troopers formed the backbone of the Republic's new military that waged war against the forces of the Confederacy of Independent Systems. So symbolic were they of the times, the galaxy-wide conflict that saw their debut took its name from their ranks: the Clone Wars.
General Grievous was a brilliant Separatist military strategist and a feared Jedi hunter, known for his ruthlessness and hacking cough. His body itself was a weapon, allowing him lightning quick strikes and devastating blows. But he was also quick to run from a fight, a tactic that worked until one final meeting with Obi-Wan Kenobi.