This is an expression is used by Army leaders. The "know" means that the leaders should be people who will sacrifice and want to learn. They must do this so that they can properly train others.
Learn and increase training--BE-KNOW-DO is the philosophy of US army program.
The KNOW part of the slogan is the idea that officers need to learn the skills for the army as well as good communication skills. The expectation is soldiers must be educated as well as trained in military knowledge. They are expected to understand world events and understand the position of the US army. They are also expected to share their knowledge and assist in training of others.
