One of the most frequently ignored rules in B/X Dungeons & Dragons is that two-handed weapons always lose initiative. I'm not going to defend the rule here. I'm going to explain how to use two-handed weapons if you don't ignore the rule.
This next monsters up in my series on B/X monster tactics are likely to have two-handed weapons, and they would definitely know how to use them effectively.
First Things First
So far as I can tell, the 1981 rule book isn't entirely clear about whether two-handed weapons lose initiative when you aren't using variable weapon damage. If you're not using variable weapon damage, though, then you probably shouldn't make two-handed weapons lose initiative either. I'm going assume variable damage.
The two-handed weapons are the crossbow (1d6 damage), battle axe (1d8), two-handed sword (1d10), and pole arm (1d10). Fighters, Elves and Thieves can use them all. Dwarves can use the crossbow and battle axe. Halflings can use the crossbow.
Not everybody is cut out for using two-handed swords, pole arms, or battle axes. For one thing, you can't use them with a shield. So, you might want to avoid them if your Dexterity isn't at least 13, giving you an AC bonus that's at least like having a shield.
Second, when you use a two-handed weapon, your risk of giving your enemy first strike against you. So, a good AC, a lot of hit points, a high Constitution score, and/or a Dexterity of 16 or better would also be desirable. As we'll see, the risk of getting hit first is greater in the dungeon than outside, so you might consider reserving two-handed weapons for outdoor use.
Other editions restrict their options, but in B/X, thieves can use pole arms, two-handed swords and crossbows, and they can (arguably) gain the benefits of striking unnoticed from behind when they do so. More on that later.
Who Cares if You Lose Initiative?
When you use a two-handed weapon, you lose initiative. That's a bad thing, right? It's the cost of dealing 1d10 damage instead of the measly 1d8 you'd deal with a sword. Isn't it?
Sort of. The thing is, 1d10 vs. 1d8 is only 1 more point of damage per round on average, and not all the two-handed weapons deal 1d10 damage. The battle axe deals 1d8 (same as a sword), and the crossbow 1d6 (same as a short bow)!
However, losing initiative isn't necessarily a bad thing. As any war gamer can tell you, there can be benefits to moving second, after the enemy has already moved and you've seen where they went. Consider this situation:
Pico the Fighter has a sword and shield, and he's encountered Orko the orc, who has a sword. Pico is AC 2 and moves 20' per round (plate mail + shield). Orko is AC 6 (leather armor + shield) and moves 40' per round. They are 70' apart. Who gets strikes the first blow?
Round 1: Pico wins initiative and moves 20' closer to Orko. Orko moves 5' closer to Pico. Their distance is now 45'. (If Orko wins the initiative, he still should just move 5', answered by Pico's move of 20' or less.)
Round 2: If Orko wins the initiative, he moves in and gets the first blow. If Pico wins the initiative, he still can't make it all the way to Orko. Orko will close the distance on his side's turn, and Orko gets the first blow against Pico.
Their speed difference means Pico can't get the first blow unless the encounter starts with Orko 25' away or less. Otherwise, Orko can always end his movement 45' from Pico until he is able to close in and get the first blow. And that's with Pico using a normal sword and rolling initiative. If Pico has a two-handed weapon, he'll lose the initiative every time, but it works out the same. The orc gets first strike against him.
The Lesson: If you're already slower than the enemy, they'll get first melee strike against you whether you have a two-handed weapon or not. Losing initiative doesn't cost you much.
And The Lesson applies both ways. If you're faster than the enemy, you can have first strike against them whether you have a two-handed weapon or not. You just need to start the round close enough to move to the enemy but too far for the enemy to move to you. The only way they can avoid giving you the first strike is to back up out of your range.
So, first strike in melee depends more on who is faster, not on initiative. Unless the encounter starts with the enemy already within your movement. That will happen more often in the dungeon than outside. If you're slow and you want a chance to get the first strike in the dungeon, don't use a two-handed melee weapon. If you're slow and you want the first melee strike outside, just forget about it. You won't get it even if you use a one-handed weapon.
Fighters, Dwarves and Elves
If you're a Fighter, Dwarf, or Elf, your movement is probably 20' per round due to your metal armor. You are slow.
Here's what happens if you have a one-handed weapon and the enemy is just as slow as you are. The enemy should stay more than 25' away from you until they lose initiative. Then they should end their movement 25' feet from you. In the next round, if they win initiative, they can close and strike you first. If initiative is tied, they can close and strike you, but you will get to try to hit them too. You can have first strike, but only if you win initiative. Of course, you'll be trying the same thing. So, in effect, after the first round you'll be 25' apart (if possible), and first strike will go to the initiative winner in round 2.
With a two handed weapon, the enemy never loses initiative. So, they can't wait to close until they've lost initiative, hoping not to lose it the following round. They just have to close. But if they end their movement within 25' of you, you can close the distance and get the first strike. If their speed is the same as yours, and the encounter distance is 30' or more, they have to come that close if they want to attack you. They had a chance of getting the first strike against you when you had the smaller weapon, but now they don't. All you have to do is stand your ground and make them come to you. Meanwhile, your party's spell casters and ranged attackers are doing their thing.
For heavily armored Fighters, Dwarves, and Elves, then, the two-handed melee weapons have a defensive function against enemies the same speed as you (usually other heavily armored attackers). They have to give you the first attack if they want to close to melee. Against faster enemies, it's a moot point; they're going to get the first attack no matter what. Still, it might take them an additional round to get to you, as they avoid ending their movement within 25' of you.
I think this solves some of the mystery of the battle axe. Why would anyone choose battle axe over weapon over a sword, which allows a shield and doesn't lose initiative every time? If you're a Dwarf, though, it's the only way you can gain guarantee yourself first strike against enemies the same speed as you. You're too small for a two-handed sword or a pole arm.
Not a lot of monsters have a speed of just 20', though. So, most of the time, all you're doing is slowing the enemy advance, not guaranteeing yourself the first strike. Your allies should take advantage of that with spells and missile attacks. Your job is to be the threat who makes them pause 30' or 35' away from you, rather than coming close enough for you to swoop in and hit them.
Skirmishing with Crossbows
It's unrealistic, but crossbows are the ideal skirmish weapons, especially for halflings and thieves. Ranged skirmish tactics rely on "the old scoot 'n shoot." You move to a place your enemy can't reach you, and then you shoot them. Repeat until the enemy is dead.
That maneuver is much easier if you know that you and your enemy will be alternating turns throughout the fight. Yes, the crossbow-wielder is yielding initiative in the first round, so they definitely don't want to start the fight within their enemy's movement range. But after that, so long as their enemy isn't faster than them and they have room to maneuver, the enemy can't catch them if they spend each turn moving away and then shooting.
With a longbow or short bow, you have to be twice as fast as your enemy to guarantee they won't be able to catch you. That's because your enemy might lose initiative one round and win initiative the next, effectively getting to move twice before you get to scoot. Archers with bows need to be unarmored, and facing enemies with metal armor, to skirmish.
With a crossbow, you don't have to be twice as fast as your enemy. You just need not to be slower than them. Crossbowmen in leather armor can skirmish effectively against any enemies with 30' or less of movement per round.
Did I mention that crossbows have the longest range of any missile weapons: 80' for short, 160' for medium, and 240' for long? Because crossbows have the longest range of any missile weapons. They can be great weapons.
If you're a Halfling, you get +1 to all your ranged attack rolls, and you can hide well outdoors. You make a very good crossbow ambusher/skirmisher. However, your ability to skirmish will be limited if your armor is heavier than your enemy's.
If you're a Thief, you also make a good crossbow ambusher/skirmisher. The ambush option is especially nice if you can manage to attack unnoticed from behind. Many DMs don't allow Thieves to benefit from striking unnoticed from behind with missile weapons. But in a game that allows it, that +4 to hit and double damage is always welcome.
Of course, Fighters, Elves, and Dwarves can also skirmish with crossbows. They'll be much more effective in leather or no armor, though. In metal armor, any enemy with 30' of movement will eventually be able to catch them, since they can "scoot" only 20' at a time.
Thieves
In my opinion, Thieves are better able to enjoy the benefits of two-handed weapons than any other class. They can't use shields anyway, so they don't have the option of better AC with a different weapon. They are restricted to leather armor, which means they'll easily have the speed to be effective skirmishers.
And then there's striking unnoticed from behind: +4 to hit and double damage.
If the DM allows it, a thief should use a crossbow for this at every opportunity. That's especially true because the "opportunity" is probably that the enemy is engaged in melee with one of your allies in front of them. Even if they did want to come attack you the round after you shoot them, they'd have to retreat and risk an attack from your ally at +2 to hit.
(Be careful: Your DM might use "friendly fire" rules, which could discourage that tactic.)
But the melee strike from behind with a pole arm or two-handed sword shouldn't be underestimated. You just have to do it right.
In the ideal case, your strike will kill the enemy. Then there's no question of them making a return attack. It's also good for there to be someone else engaged with the enemy in melee—someone they may want to attack instead of you when they get their turn.
If the enemy does survive your attack, though, you must remember that that attack is a one-time thing. Either drop your weapon immediately or (if the DM allows it) simply declare that you won't be using it next round. If you have an ally on the opposite side of the enemy, declare a retreat (if your hp are good) or fighting withdrawal (if they aren't) for the following round.
In the next round, there's a 42% chance the enemy will win initiative and be able to attack you before you can move away. But 58% of the time, you'll win or tie on the initiative, meaning you can move before the enemy attacks. That's why your ally on the other side is so useful. Your enemy can't avoid attacks from them in those cases. If the enemy has to retreat to get to you and attack, they'll give your ally +2 to hit them.
Some DMs require monsters to declare retreats before the initiative is rolled. In those games, the monster probably won't be retreating to catch you anyway, and you'll be able to get away scot free.
I can't say that's all better than just making strikes unnoticed from behind with a normal sword. Really, it's normal tactics for Thieves. Here's the only difference. Normally, a Thief should wait until they lose initiative to make their strike. Otherwise the enemy is guaranteed a return blow that round if they survive. With a two-handed weapon, the Thief doesn't have to wait, because they will be losing initiative for certain. They can then drop the weapon after striking, and they'll have that same chance of getting away before the return attack that a thief with a one-handed weapon would have.
Your Backup Sword
Eventually, you are going to be already engaged in melee. You've made a strike (hopefully the first strike) with your two-handed weapon. What next? Do you keep using it, ceding initiative every round, or do you switch to another weapon?
I favor dropping the two-handed weapon and switching to something else right away. You've just lost initiative. Switching to another weapon reduces your per-round damage output, but it reduces your chance of losing initiative in the next round to either 42% or 50%. (The chances depend on how the DM handles tied rolls. I like simultaneous initiative on ties, so, for my game, it's 42%.) You're going to want a sword (or short sword, for Halflings) to use as soon as you're engaged with the enemy. Your two-handed weapon is good for one attack. Then you drop it and use something faster.
Are Two-Handed Weapons Worth It?
Maybe. Two-handed weapons give you some options you don't have with one-handed weapons. They let you take advantage of having a set initiative order in which you know you will get a turn after each of your enemy's turns, throughout the battle. Depending on your risk tolerance, that might be worth not using a shield. Since Thieves can't use shields, two-handed weapons are especially attractive to them.
Here are some considerations about all the two-handed weapon types:
- Crossbow: This is the skirmisher's weapon of choice.
- Battle axe: Only of use to dwarves who want the benefits of two-handed weapons described above.
- Two-handed sword: Magic ones are nice, and you may be able to use them in some places where pole arms aren't practical. Otherwise, pole arms are just better.
- Pole arm: All the benefits of the two-handed sword, and they can be set against charges. Plus, some DMs let you attack from more than 5' away with them. These are the non-magical two-handed melee weapons of choice for Fighters, Elves, and Thieves.