It seems to me (correct me if I'm wrong) that the optimal way to hold a polearm for thrusting would be with the left hand forward (assuming you're right-handed) and vice versa for cutting.

So how were polearms that can both cut and thrust like halberds and bills usually held? Did people change grip for cutting and thrusting or just stick to one?

Why the left hand forward for thrusting? If you're a right hander, that will reduce your reach if you pass with your thrust, and if you lunge you'll be lunging on the left leg.

Regardless, the answer is both 1) a bit variable by period and 2) often variable by manual. Wiktenauer has some excellent material that might be useful for investigating this.

Adam,

For a right-hander, holding a polearm with the left hand forward is a very natural stance, and is seen in art and is also covered in the manuals - Ringeck's section on harnisfechten covers both the use of the spear and sword in this manner.

First, consider that if you are in a ready stance, or are in a guard/ward which favors your dominant side... and this happens to be the right side for most people... you will have the right foot back and the left foot forward. If you want to keep the point of the weapon in position to engage the adversary, you must hold onto the haft of the weapon with your right hand aft of the left. This position also provides some protection to the dominant side at the expense of the left.

Furthermore, consider that having the hands in order opposite to the norm with a two-handed sword is not so bad with a polearm, seeing as many can be in excess of 8 feet in length. If you want reach with the weapon (which you probably do... seeing as you are using both hands), you can use your dominant side to manipulate the rear of the weapon like a tiller; this may be advantageous, as your dominant side is often stronger than your off-side. This lets the off-hand - the left in this case - hold the weapon closer to its center of mass, where the apparent weight of the weapon is less.

Now, as you noted, the right-hand-aft approach does not lend itself well to the passing step, at least in the context of unarmored combat. This is not to say that it cannot work well in that regard, either. As you insinuated, there's nothing really holding you to do one thing or another - it should just be a question of what you want to do, how the weapon in question works, and what works best for what you want to do with the weapon at the time. If a long cut, or a marginally greater reach is important, perhaps you should stand with the right foot forward in a polearm equivalent of the longpoint. Keep in mind that if you do so, you loose the often more forceful push of your right side to strike at an adversary.

Even for thrust-only polearms, we have evidence for considerable variation in how they were held. Many (but not all) pictures from the 15th and the early16th centuries show pikes held with the right foot and right hand forward, while in the late 16th and the 17th centuries pikes were predominantly (but again, not always) held with the left foot and left hand forward.

You want to be able to switch between grips.

I'll usually fight with polearm with right hand leading. In this way, I fight in a similar way with polearm and greatsword (and longsword) - I'm right-handed and hold the sword with right hand leading. Where I find it makes a large difference is when fighting against sword and shield (or other short weapon and shield). Right hand forwards on the haft means the haft is on my left, and it will protect me better against the sword of a right-handed sword and shield fighter. Also, it's easier to try to come around on the inside of the shield into the torso, while still being easy enough to go over/under into head/thigh on the outside,

I've found this polearm on the opponent's weapon side when fighting sword and shield to make enough difference to switch polearm grips for fighting left-handers.

Other than against shield, it makes less different. Against one-handed single sword, you might want to be the other way, but you have an overwhelming advantage, so you can fight either way with success.

Against another polearm, same grip or opposite grip to the opponent makes a difference, but it's symmetric.