You may sheath or ready a weapon that you have Expertise in. You may only perform this feat once per turn.
When you roll Initiative to begin an encounter, you may use this maneuver as an immediate reaction to ready a weapon, shift one square, then make a basic attack with that weapon against a target that rolled a lower Initiative result than you.
When you perform an opportunity attack, you may use this maneuver to draw a weapon before you make the attack. If you do, you gain advantage for that attack.