Strength

The Strength attribute enhances a Warrior's when using attack skills. This is a primary attribute and may not be used by secondary warriors.

Guild Wars Description
When you use attack skills, each point of Strength gives you 1% armor penetration. Many skills, especially those related to surviving and inflicting damage, become more effective with higher Strength.

General Description
Strength relates mainly to stances and shouts aswell as a few attack skills.

Strength is a requrement for meeting some max defence shields.

Even if a Warrior does not utilize any Strength skills, it's recommended that any spare points be placed into Strength, if only for the purpose of dealing a little more damage when using attack skills.

Associated skills
Strength will enhance these listed skills strength skills.