As a commander your tools and your devices shall be myriad, yet the wise man knows that battles are won by flesh, not the machine. Flesh can learn, whilst the machine must be forever instructed. Flesh knows loyalty to its brothers and the veneration of the Emperor, whilst the machine knows not these things.
Whenever the day is darkest and victory is in doubt, look not to the machine for aid, but to your Battle-Brothers. The machine can only bring you victory if you tell it how such a thing can be done. Your brothers will walk through fire, they will stride through the most terrible carnage at a single word from your lips, and they will bring you victory simply because you ask it of them.
— The Codex Astartes, Warhammer 40,000