This pose is more about balance than actual fighting pose like Warrior I.
From Mountain pose step one foot back about 3 and half feet. Slowly bend your torso forward while simultaneously extending clasped arms and raising your back leg. The leg that supports your weight should be straight with locked knee. Continue to bend and rising you back leg until they are in line and parallel to the floor. You should look straight ahead your head should be above the shoulders (see the picture).
This pose looks like one of the Kung Fu poses with a sword. If you think about it greatly extends sword's reach.
