This blog is a comparison between the various types of polearms for the current discussion about spears/javelins/pikes/lances. Polearms were the most popular melee weapons of armies of all times, ending with the bayonet which turns a musket into a short spear.
Wikipedia defines polearms as "a close combat weapon in which the main fighting part of the weapon is fitted to the end of a long shaft, typically of wood, thereby extending the user's effective range". Based on this definition it is still discussed if spear-like weapons are also included or just helbards, longaxes etc. But I will use the term "polearm" as a collective term for all weapons with a pole as an important part. I will only mention weapons used in European warfare.
Javelin[]
Javelins are spears that are balanced as throwing weapons. They are either thrown by hand or by a spear throwing device.
Pilum[]
The pilum was the javelin used by the Roman army. But as with everything about Romans, nothing general can be said about it because there were lots of different types of the pilum. Some were designed to stick in the shield of the enemy (since at that time shields were the most important factor of infantry), others tried to penetrate the shield to stab the soldier.
Short Spear[]
Spears were since the bronze age used as light personal melee weapons, usually combined with a shield, for example by Numidian infantry or Zulu warriors. These spears were mainly thrusting weapons but could also be thrown. Short spears were the most popular weapon in stone age and bronze age battles.
Long Spear[]
The ancient Greek hoplites used spears with a length of over 2m (7 feet) as main melee weapons but never as throwing weapons. They were used in one hand with the shield in the other. The hoplite could attack with the spear through the shield wall. These spears also had spikes at the other end that could be used to stand the spear in the ground.
Other uses of a spear-wall include the Roman triarii, the Scottish schiltron, and the infantry square formation of the Napoleonic era. All in all, this formation had a very good defense as long as the formation is unbroken.
Pike[]
The Macedons under Philip II reformed the Hellenistic battle tactics and exchanged the spears with pikes of almost the triple length (the sarissa). These pikes could be used to form a pikewall, an almost unpenetrable defense against cavalry and enemy melee troops. Such a formation could only effectively be breached with massed ranged attacks or charges of elephants or scythed chariots. But the length of the pike made it unuasable for any fighting outside of the formation and such a formation could not adopt to enemy flanking.
In the late medieval and renaissance era, the pike again became popular as infantry melee weapons. It was easy to produce and pikemen were easy to train. These pikes could stop any cavalry charge and were used to protect musketeers (this was called a "pike-and-shot" formation) but the superior range was also used to fight enemy non-pike infantry with great efficiency. In the best formations, 4 to 5 pikes per row could point at the enemy at the same time. A rare tactic to defeat a pike wall was the use of double-handed swords to break the pikes.
Mounted Spears and Lances[]
Cavalry from early on used spears as thrusting or throwing weapons. Spears used as thrusting weapons allowed the rider to use his speed as advantage on impact with the enemy. The first spears were used one-handed. Over the time the length of the spears increased and some were used with both hands.
The cataphracts (heavily armoured cavalry in heavy formation) were the first to use a lance, a longer and usually two-handed weapon that was expected to break on impact. In some cultures it was seen as dishonourable if the lance was still intact after a battle because that means it was never used. In feudal and medieval ages the lance became the most popular melee weapon of heavy cavalry (eg. men-at-arms, hussars). The lances used by knights were usually one-handed and locked under the arm to put all the speed of the rider into the impact. As secondary weapon (after the lance broke) many troops had long swords.
The word "lance" is sometimes misused for spears used by infantry.
Halberd[]
Halberds are polearms with the spike of a spear, the blade of an axe and a thorn at the backside of the axe blade. Best known for their use of halberds were the early Swiss Gewalthaufen which was known for being almost invulnerable (and defeated much larger and better equipped forces many times). Halberds have the range of a spear but also the penetration of an axe. The thorn was designed to draw knights from the backs of their horses.
Anything else[]
There are countless polearms I didn't mention here: Longaxes, warscythes, glaives...the list goes on and on, without even leaving Europe. There are so many polearms that it's pointless to separate between them all. Instead we should categorise them by their function. Medieval melee polearms for instance have four different functional head parts: spikes for thrusting, blades for slashing, hammers for shattering, and hooks for pulling. Some weapons combined multiple heads; for example a halberd usually has an axe blade, a spike at the top, and a hook for pulling enemy knights down.
The glaive deserves a special mention here because the weapons used by high elves are very similar. A glaive is a polearm with a single edged blade as head. The blade is often slightly curved. It is used as a slashing weapon.