Most people know that muscles contract when they receive an electrical impulse. So is a brain really necessary? Every way I can think of that a human or animal can die is a result of the brain ceasing to function. If your heart stops working, the blood stops flowing, thereby cutting off the food and oxygen flow to your brain, and you pass out and eventually die. If your lungs stop working, your blood doesn’t receive oxygen, so it carries food to your brain, but not the oxygen needed to process it, so your brain runs out of energy and you pass out and die.
So what if you replaced the brain with electrical circuitry, or used some kind of neural helmet to stimulate impulses from the brain? You could raise bodies from the dead. The person would still be dead, but the body would be functional again. Add an AI and you have a semi-intelligent zombie or a recycled body, however you wish to think about it. Also, suppose you programmed the circuitry and added a radio (or other wavelength) transmitter and receiver? You would have a remote controlled human.
Now, suppose we had nanobot technology. We could program nanobots to take over a brain, thereby creating the same effect as the helmet in the last paragraph. While we cannot do this with current science, it is a much more useful form. You could package the nanobots together in projectile form, and create a weapon that would turn the enemies to your side instead of killing them, creating an army that grows with every casualty it inflicts.
There are a few obstacles to the use of this idea. First, if any other vital functions were compromised, the body would not live very long. Take the heart or lungs, for example. The body would only last until the muscles ran out of energy from lack of oxygen. Also, I highly doubt we understand the brain fully yet, and for this idea to work, we would either have to duplicate all of the brain’s functions exactly (in the case of replacing it with circuitry), be able to take control of specific parts of the brain (in the case of the nanobots and helmet when used on living people), or be able to stimulate every part of the brain and take specific control of specific parts of it (in the case of the nanobots and helmet when used on dead bodies). I doubt any of these are currently within the reach of today’s scientific community, but I would not be surprised to see us gain those abilities during this generation.