That was with low-level PCs in mind, though. Once the PCs gain several levels, they begin to rival the great monsters, at least at a glance. A 6th-level fighter has about as many hit points as a white or black dragon, and maybe more if he has a bonus from Constitution. Most likely he's going to have as good or better AC than most dragons, too, with magical armor and shield bonuses. Dragons usually have the edge in physical attacks (a lowly white dragon has damage potential of up to 24 points per round, compared to the fighter's 1d8 or so plus Strength and magic - say, around 12 points max. The dragon theoretically has an advantage in attack rolls (14 to hit AC 0 for a 6 HD white dragon) but a fighter at 4th level probably has similar odds (base 17 to hit AC 0, but with a combined bonus of +3 or more from Strength and magic, he at least equals the dragon.)
(Random digression: This, in my mind, is a good argument in favor of limiting attack and damage bonuses from magical weapons.)
A B/X white dragon has 6 Hit Dice, an AC of 3 (equivalent to plate armor), and damage of 1d4/1d4/2d8 with its claw/claw/bite attack routine. That's pretty tough for low-level PCs, but curiously, except for the better AC, ability to fly, and breath weapon, it's not far off from the stats of a tiger (6 HD, Dam 1d6/1d6/2d6) -a formidable foe, to be sure, but less than you might think. While the correlation between size and HD in B/X is tenuous at best, taken together with attacks and damage it maps pretty well to size and strength. The dragon's claw attacks do as much damage as a character with a dagger, and less than the tiger's claws. Its bite is a little better than the tiger's, but the total damage potential is 24 in both cases.
(Random digression: A 3 HD giant crab also has damage potential of up to 24 points - 2 pincers for 2d6/2d6. An overgrown crustacean is going to mess you up as much as a tiger or a dragon? What?)
So, apparently a white dragon is roughly equivalent in size to a tiger. Probably a longer, more sinuous shape, with smaller claws and bigger teeth, but still pretty close to the same overall bulk and strength.
More powerful dragon types have more Hit Dice, better ACs, and significantly more powerful physical attacks, but across the board, a dragon's biggest advantage over other foes is its breath weapon. This inflicts automatic damage (no attack roll needed) equal to the dragon's current hit points, or half that if a save is made. In theory, then, our white dragon could either knock a 6th level fighter (or a group of them - breath weapons are area attacks!) either to around 0 hp, or to around half their starting hp in one breath. Lower level characters would most likely be slain outright on a failed save, and in very bad shape even on a successful save. A dragon can use its breath weapon three times per day, so if it doesn't wipe out the opposition on the first try, it can finish them off with a second blast.
Of course, if the PCs get the drop on the dragon - either surprising it or winning initiative the first round - and manage to do some significant damage to it, they also reduce the damage it can do with its breath. This is virtually essential for successfully fighting a dragon. More so than in almost any other situation in the game, surprise and initiative can make the difference between victory and a rout or TPK.
Clearly, then, these B/X dragons are not the gargantuan monsters depicted in fantasy art (including that of most editions of D&D.) They aren't Smaug. (The Mentzer edition Companion set provides stats and write-ups for such epic beasts, though they should probably be exceedingly rare, maybe no more than a small handful in an entire campaign world.) While they are physically robust and well-armored, B/X dragons aren't world destroyers. If they were no more than their physical bulk, armored hides, claws, and teeth, they'd be tough, but predictably beatable by a party with enough experience.
Even more than their legendary breath weapons, it's the intelligence and cunning of dragons that truly set them apart from run-of-the-mill monsters. Dragons should absolutely not be played like zombies, charging headlong into battle and fighting until slain. A toe-to-toe fight between a powerful party and a dragon should almost never happen. Even dragons not intelligent enough to talk or use magic will be clever and devious opponents. A party that expects to walk into a dragon's lair and cut it down through sheer force of arms and magic should generally have a very bad time, even if every one of them individually has more levels than the dragon has Hit Dice, because dragons play their advantages to the hilt. Defeating a dragon should require them to outfox the beast, not merely outfight it.
If there were a book like The Art of War written by dragons for dragons, it would probably include the following pieces of advice:
- The first strike is decisive. Be aware of your opponent before he is aware of you.
- Whenever possible, observe and learn the strength of your opponents. Engage them in conversation, if you can talk, and if you can do so without endangering yourself unduly. Humans who come poking around in a dragon's lair are either very formidable or very foolish, but the greatest fool is you if you mistake one sort for the other.
- Your lair is your fortress. Know it to the last detail. Set traps and alarms on every entrance, especially if you plan on sleeping there. Block the entrances that are of no use to you. Conceal the others if possible, and consider moving if you can't.
- Unite and conquer! Use terrain to your advantage, to force your enemies to approach you together so that you may wipe them out at once with a breath attack. Do not allow them to surround you and bring all their attacks to bear on you at once. Hallways and narrow defiles are your allies; huge chambers with low ceilings are deathtraps.
- Choose the time and place of a fight to suit you. Don't fight on your enemies' terms if you can help it. Outdoors, the choice is almost always yours, because you can fly.
- Use your wings. When fighting outdoors, don't stand there on the ground while your enemies swarm over you. Take to the air; use your mobility to attack individuals separated from the rest, and take off again before the others can come to their aid. If you've chosen a particularly spacious cavern for your lair, you can use flying tactics there too.
- Employ henchmen, hench-monsters, servitors, dragon cultists, etc. to act as guards, spies, and providers of tribute in the form of treasure and fresh meat. Don't ever trust them completely, though.
- If you have the use of magic spells or items, use them, especially if they facilitate one of the above strategies.