What is the theme in Rogue Warrior by Richard Marcinko?

The end justifying the means is a major theme in the book. Richard Marcinko is clear that he is willing to fight a dirty war. His only interests are to get his men out alive and kill as many of the enemy as possible. To do this in Vietnam, Richard is willing to interrogate and torture prisoners for information and kill people who may not be enemy soldiers. In a civil war such as in Vietnam, there is a fine line between enemy combatants and civilians, and Richard implies that many times he may have crossed it. Likewise, Richard is willing to resort to extreme training methods in order to get the men of SEAL Team Six and the Red Cell prepared for their mission.