"What you know does not matter - what you do matters. Physical training produces physical memories - not simply muscle memory but a psychophysical imprint, knowledge that is instinctual rather than intellectual. This is useful knowledge. Automatic (instinctive) action and reaction is always faster and more energy efficient than intellectually induced action or reaction. There's already plenty to think about in confrontational situations so any response that does not require conscious thought spares intellectual energy for decisions and actions that do demand it. Train yourself to the point that particular, common actions and responses may be executed automatically.
Any deficiency in physical fitness affects confidence. When an individual realizes he does not have the fitness or skill to accomplish a particular task, or that he cannot use his tools to their utmost self-doubt weakens both intellectual and physical abilities. Flagging confidence limits flexibility, preventing appropriate adaptation to various situations. Confidence allows the audacity of original thought. Again, train such a variety of energy systems (types of fitness) that confidence in the face of any challenge is reflexive.
Strength + Confidence + Flexibility = Strategy (the ability to use it).
Physical fitness relative to the mountain environment or to any situation (physical and psychological) can have positive or negative effects on the individual, his teammates, and the overall strategy chosen to accomplish a particular goal. Get fit and stay fit to accomplish a variety of tasks. The goal of physical training can be summed up in one phrase, “to make yourself as indestructible as possible.” The harder a man is to kill, the longer he will remain effective, as a climber, a soldier, or what ever.