"The Orks plague the galaxy from the end to end with their ceaseless warring and strife. They are a race rooted so deeply in war that peace is utterly incomprehensible to them. They cannot be bargained with or bought save with weapons that they will inevitable turn against those who tried to bribe them. I pray with all my faith that some great catastrophe will annihilate them but I fear that ultimately it is they, not we, who shall rule the galaxy."
Imperial High Lord Xanthias
The Ork physiology is simple and robust made to allow Orks to survive the most horrendous injuries and still come back for more.