Pikes are sort of the inverse of cavalry. (Last considered here.) As we might say -- considering its most advantageous mode -- Pike attack is intrinsic to the enemy's movement. When used on defense, all of the impetus that a charging attacker might generate (preeminently: cavalry) is turned back on the attacker himself.
Quotes to Consider
The use of pikes (in the general sense of extremely long spear-like weapons) went through several long cycles of use historically -- first by the ancient Greek hoplites in their phalanx formation (where the long weapon was called the sarissa), and later by the medieval Swiss and German landsknechts (where the weapon was in fact called a "pike"). Late in the period, pikes were used in various mixed formations, such as pike & halberd, pike & crossbow, pike & shot, etc.
The general consensus seems to be that pikes did a spectacular job on defense, obviously being able to present a dense thicket of points at great distance to the enemy. In particular, the re-discovery of their use in the Middle Ages was specifically in response to the dominance of European heavy cavalry. The disadvantages seemed to be: they needed an exceptional level of drill and discipline to be used as an effective unit (to march, support, and not get tangled up on each other), they were somewhat more difficult to use in an offensive attack, they were particularly vulnerable to loss of cohesion in cases of rough terrain, and they were overall less flexible in their use than other types.
Robin Lane Fox writes this description of the Greek phalanx in his biography Alexander the Great:
Sarissas were to be held erect and on command, the first five ranks were to lower them for the charge and swish them in perfect time from left to right... On the first rapid strides forward, the main enemy fled in panic from the hill-tops, scared by the disciplined drill and the sound of the war-cry. [Alexander the Great, p. 84]Two classic examples which highlight the weaknesses of pike are the Battles of Pydna and Cynoscephalae, in each case seeing otherwise strong Macedonian phalanx-type units lose out to Roman sword-and-shield bearing legionnaires when they met on rough or confused terrain. C.W.C Oman, in his Art of War in the Middle Ages, refers back to these battles when discussing Swiss pike vs. Spanish sword battles in the 1500's: "the old problem... was once more worked out... Then, as in an earlier age, the wielders of the shorter weapon prevailed." [p. 108]. He then quotes from Machiavelli's Art of War:
When they came to engage, the Swiss pressed so hard on their enemy with their pikes, that they soon opened their ranks; but the Spaniards, under the cover of their bucklers, nimbly rushed in upon them with their swords, and laid about them so furiously, that they made a very great slaughter of the Swiss, and gained a complete victory.Oman then continues:
The moment a breach had been made in a Macedonian or Swiss phalanx the great length of their spears became their ruin. There was nothing to do but drop them, and in the combat which then ensued troops using the sword alone, and without defensive armor, were at a hopeless disadvantage... Machiavelli was, from his studies in Roman antiquity, the most devoted admirer of the Spanish system, which seemed to bring back the days of the ancient legion. Yet even he conceded that the pike, a weapon which he is on every occasion ready to disparage, must be retained... He could think of no other arm which could resist a charge of cavalry steadily pressed home... [Oman, Art of War in the Middle Ages, p. 110]
Rules from Chainmail
Chainmail has several special rules for pikes in its mass combat section, including this one: "All troops formed in close order, with pole arms, can only suffer frontal melee casualties from troops armed with like weapons. While a Knight armed with a lance could attack a halberd formation, he could not attack a formation of pikes." [CM p. 40: Combat Tables]
However, the man-to-man combat section is almost silent on the issue. On the first turn, troops with long weapons get the first blow, while on later turns the opposite is true. [CM p. 25] This is adjudicated through numerical weapon "classes" in the man-to-man combat tables, higher numbers indicating longer, heavier weapons (1-12, with pikes of course being the maximum).
There is also a fairly complex series of cases for possible parry options and multiple attacks based on differences in weapon class [CM p. 25-26] -- broadly familiar to AD&D players because it formed the basis for similar rules in the DMG vis-a-vis weapon speed factors [DMG p. 66]. No other comment on number of ranks attacking, or any "cooperative" benefit from anyone other than the single person in man-to-man combat, is made in any of these sources.
On Number of Ranks Attacking
For the function of pikes, the number of ranks that can reach the enemy and attack seems like a fairly important (perhaps all-important) issue. However, sources such as Chainmail, Original D&D, or the AD&D PHB/DMG do not mention it at any point. OD&D Sup-I says of pikes in a footnote, "these weapons are not usable in dungeons as a general rule due to length" [Sup-I, p. 15], and leaves it at that; likewise, the AD&D DMG says, "Such a weapon [pike] is not usable in dungeon settings, or anywhere else without masses of other pikes to support it." [DMG, p. 66]. In Gygax's Swords & Spells mass combat rules, two ranks of pike attacks are possible [S&S, p. 17]; in Doug Niles' Battlesystem, three attacking ranks are allowed [BS1 p. 14, BS2 p. 40]. Again, the longer weapon always gets first strike opportunity, but no other mechanical benefits.
Compare this to historical sources which state that as many as four or five rows of pikes would have their points ahead of the front line, for use against the enemy. For example, see the Fox quote above regarding Alexander's forces. Or again, Machiavelli:
Although I have told you that six ranks were employed in the Phalanxes of Macedonia at one time, none the less, you have to know that a Swiss Battalion, if it were composed of ten thousand ranks could not employ but four, or at most five, because the pikes are nine arm lengths long and an arm length and a half is occupied by the hands... [Art of War, p. 71]
On the Shock of Mass Pikes
A recurring point among many sources is that a properly-formed pike square is practically unreachable by a foe without an equivalent weapon or some type of special advantage. For example, here's one description of the battle of Pydna:
Paullus [the Roman commander] claimed later that the sight of the phalanx filled him with alarm and amazement. The Romans tried to beat down the enemy pikes or hack off their points, but with little success. Unable to get under the thick bristle of spikes, the Romans used a planned retreat over the rough ground. [Wikipedia: Battle of Pydna]However, probably the biggest weakness of classic OD&D or AD&D man-to-man combat rules is that they are all explicitly written to be just that: adjudicating one man fighting one other man, exchanging blows each round. Although the man with longer reach is given first blow in the first round, there is no allowance for any of the other, supporting men around him to assist in any way. Also: Even in the case of a "hit" there's no rule to prevent continued forward motion by the attacker and delivery of his attack.
Moreover, even if we assume that a man charging at a pike square runs past 3-5 pike tips (and associated interrupting strikes), the chance for a normal man to hit in D&D is so low, it likely won't keep away an attacker for very long. Consider OD&D 1st level fighters, with the attacker in chain & shield (AC4); the chance for one pike-defender to hit him is only 30% (6 in 20). If the attacker runs past 3 such pike-tips, there's still a 1-in-3 chance that he moves in totally unscathed (0.70^3 = 0.34%)! And if the first charger doesn't manage to make contact, then clearly one of the next few attackers will quickly be among the pikes. That just doesn't seem right.
On 3E Reach
3E D&D makes another design decision that at first blush seems reasonable: To generalize the idea of "reach" advantage, such that anyone who can strike at a distance -- whether pike-armed men or giant monsters -- will function the same mechanically [PHB p. 122].
However, upon further reflection, the two situations are really not comparable. For the pike, the defensive benefit is that it is fixed, pointing straight ahead and still; the enemy can thrust himself on it at any time and the tip will be there to intercept him. But for a large creature like a club-armed giant, blocking an attacker must require a properly-timed swing, presumably in a great swooping arc, and one would think it unlikely that it would be timed quite right against a charging hero.
But since 3E allows both types of defender to get a "free attack" against any approaching attacker, we arrive at a situation where giants -- usually pictured as lumbering and slow (in several senses) -- have the lightning reflexes of a master duelist, always able to snap off a riposte against fighting men running to the attack. This was, in my opinion, a greatly malformed rule -- as was giving giants several attacks per round based on Hit Dice.
Furthermore, 3E defines their interrupting attacks-of-opportunity as technically occurring when a character moves out of a threatened space -- which makes some design sense, as they didn't want a normal sword-vs-sword attack to trigger the action. However, it's greatly counter-intuitive in the case of a defensive pole-weapon, in which you'd think the dangerous stroke comes as you move into the pike-tip zone, and once you are past it you are by definition inside the shaft and unable to be hit.
Finally, the 3E system specifies by default that any defender only gets one such attack-of-opportunity per round (without some special and rarely-taken Feat), such that any follow-up attackers after the first can move in absolutely unimpeded. Again, this makes no sense in the context of a pike, simply being held straight out and forward, such that it is in the path of any onrusher who might approach.
In general, I feel like the 3E decisions on this point are, while initially clever-sounding, in every case exactly the opposite of the correct design choice.
Some Suggested Fixes
In light of the foregoing, we might look for some brand-new rules to add to the relative silence of OD&D and AD&D regarding pike formations. Can multiple ranks attack on defense (or otherwise)? Can multiple files to the side multiply this attack? Should there be a bonus to-hit, possibly from the density effect (less space for the incoming attacker to dodge to the side)? Should a non-fatal hit stop the attacker's forward progress, foiling their attack (really of minor effect, granted the low hit frequency)?
And other concerns quickly arise: Once one attacker rushes in (possibly being felled from the pikes), can other attackers follow in behind, during the same round? Do defenders get multiple interrupting attacks per round, or just one (as is explicit in 3E)? Do pikes drop victims on the ground, or hold them skewered upright (possibly blocking follow-up attackers)? Does a big pile of bodies develop, creating cover?
In my experiments, what I've found is that without some radical modifications to the base D&D rules, in most cases the result is routinely this -- a huge rush of attackers come towards the pikes, a significant number are struck down, but inevitably the attackers are in hand-to-hand combat with the pikes at the end of the very first round.
- How many ranks of pikemen can strike offensively (vary by target size)?
- How many ranks of pikemen can strike defensively (vary by target size)?
- How many ranks of pikemen can "set" for double damage?
- Do we allow an attack by pikes to "interrupt" the movement action of an opponent (even by a pikeman not individually the target of the attacker)?
- Can pike "interrupt attack" any number of attackers during a turn, or are they limited (say, to 1 as in 3E)?
- When used against charging cavalry, can the pikemen all opt to strike against the riders? (Or is it 50/50 riders/horses? Or more likely against the horses?)
- Do pikemen get a "formation bonus" to hit defensively due to closely-packed spikes?
- Does a strike by a pike vs. an attacker end the attacker's move?
- Does a kill by a pike block other attackers moving through the same zone (either by piling up bodies or "skewering" upright)?
- Do we need to establish special rules to simulate the organization/formation requirements of properly using pike?
- Do we permit heterogeneous formations (pike & halberd, pike & crossbow, pike & shot, etc.)?
- If a man drops the pike to use sidearm sword, can he later pick the pike back up?
- Do pikes cancel the cavalry rider AC bonus?
(Note: This corrects the garbled draft post I made a week or so back. The first few comments are re-posts of comments made at that time.)