Martial vigour and ferocity are virtues, to be shure. But do not throw your forces blindly into battle and say that this is vigour. It is not. Before commiting your forces, examine the situation. Review your own strength, and that of your enemy. Remember your own objectives, and try to anticipate those of your opponent. He who fights without understanding the battle he is fighting places himself at a disadvantage.

Legions Astartes, Collects of war

"Forget the promise of progress and understanding, for in the grim darkness of the far future there is only war. There is no peace amongst the stars, only an eternity of carnage, death and the laughter of thirsting gods."