|Damage vs. small||1d4+1|
|Damage vs. large||1d4|
|Base price||5 zm|
Due to its low damage in all cases, lower than the mace (a good option for priests), and the long sword (a good option for barbarians), a war hammer is generally a useless weapon, and usually only good for training the hammer skill in preparation for Mjollnir.
Average damage calculation
|Weapon||Small monsters||Large monsters|
|+0 war hammer|
|+7 war hammer|
The war hammer first appeared in NetHack 3.0.3. The lucern hammer, which existed since NetHack 1.3d, was erroneously classified as using the hammer skill rather than polearm skill. This mistake was carried over from canonical D&D, where clerics, who were restricted in most weapon classes except blunt weapons, would happily spend their entire player's career not knowing that they were thwacking away with a polearm. This led to Thunderfist, the predecessor of Mjollnir, having the base item of a lucern hammer.
Correcting this mistake, unfortunately, also greatly restricted the effectiveness of the hammer skill, as well as making Mjollnir a less effective weapon choice.
The damage of the war hammer in NetHack is most likely based on the damage it dealt in Advanced Dungeons and Dragons, which is to say, 1d4. Unlike in NetHack, or its predecessor, D&D, war hammers certainly were not puny by any account, and in fact, a quite versatile weapon; NetHack does not give them enough credit.
In the real world, war hammers, much like maces, were important for facing heavily armored opponents. The blunt hammerhead would deliver concussive force through the thickest armor, and the pick end on the opposite face could be used to punch holes, whether through a piece of armor or the odd skull. They could also be used in grappling.
Chain mail, or a chain coif, in particular, was designed as special protection against the slash of the sword—an armor type that would have no particular benefit against a war hammer wielding opponent. Plate mail rendered sword strikes mostly harmless, making most blows ricochet; the war hammer addressed this protection, being able to cause great damage even without ripping through the armor.
Unfortunately, none of these realistic mechanics are preserved in NetHack, where war hammers cannot be used to grapple in any way, nor are they any more effective against an armored opponent.
They had come together at the ford of the Trident while the
battle crashed around them, Robert with his warhammer and his
great antlered helm, the Targaryen prince armored all in
black. On his breastplate was the three-headed dragon of his
House, wrought all in rubies that flashed like fire in the
sunlight. The waters of the Trident ran red around the
hooves of their destriers as they circled and clashed, again
and again, until at last a crushing blow from Robert's hammer
stove in the dragon and the chest behind it. When Ned had
finally come on the scene, Rhaegar lay dead in the stream,
while men of both armies scrambled in the swirling waters for
rubies knocked free of his armor.