Miyamoto Musashi on facing your opponent...

"Since olden days many opinions have been expressed about which part of an opponent one should look at [during a duel] but the majority of people have supported staring at an opponent's face. When so doing, the eyes should be narrower than usual but the mind should be broad. The eyeballs should not move and when the opponent is near they should be focused as though they were looking into the distance. In this way, a man can look at not only his opponent's face but his whole body, thus being able to anticipate any offensive thrusts he might make. In my opinion, there are two kinds of eyes: one kind simply looks at things and the other sees through things to perceive their inner nature. The former should not be tense [so as to observe as much as possible]; The latter should be strong [so as to discern the workings of the opponent's mind clearly]. Sometimes a man can read another's mind with his eyes. In fencing, it is all right to allow your own eyes to express your will but never let them reveal your mind. This matter should be considered carefully and studied diligently."- Miyamoto Musashi