Phalangites (in contrast to hoplites) are professional soldier; the first soldiers who drilled in ancient Greek history.
Warning: we might possibly "abuse language" and simply use the terms "Macedonian Phalanx", "Macedonian Phalangites", "Macedonian Hoplites" as synonyms, even though this is technically not correct. It is a sloppy use (indeed, abuse) of language, but it breaks up monotony.
Macedonian King Philip II introduced many reforms, which he [probably] considered while studying under Theban general Epaminondas (from Battle of Leuctra fame). [Diodorus notes this in his Library Book XVI, Ch. 2, §2.]
Philip II also produced a brilliant innovation: use a longer spear (a pike!). The Greeks called it a "sarissa" (Gk: σάρισα) which was 16 feet or longer (4.8 meters) and weighed 15 pounds (6.8kg). [See James Romm's
Alexander's Army and Military Leadership, appendix D in The Landmark Arrian.]
Note that the sarissa broke into two components, which made carrying them (outside of combat) easier.
The Cambridge Ancient Histories (Volume 6) notes:
The distinctive feature, henceforth to be characteristic of the Macedonian infantry, who were recruited from the peasantry of the kingdom, was the long pike called a sarissa, 12 cubits (about 5.50 metres) in length and equipped, as has been learned from a find in a tomb at Vergina, with an iron point 50 cm long, together with a butt-end, also in iron, of 45 cm and a central dowel for reinforcement. Since it could not be wielded without the use of both hands, the diameter of the shield had at the same time to be reduced (possibly to 60—80 cm) and, probably for reasons of economy, the remaining dress was only a simple leather jacket and helmet and greaves of bronze. A small sword was provided in case of hand-to-hand combat. (Cambridge Ancient Histories, vol. 6, pp 686–687)
There is a clear advantage to a longer spear: more men may be involved in the spear hedge. Records indicate that the first 4 or 5 ranks were involved in combat; the others held their sarissas at 70 degrees (not vertically, i.e. at 90 degrees).
The Cambridge Ancient histories notes "The Macedonian phalanx of Foot-Guards (pezetairoi) was drawn up at a depth of eight, ten or sixteen, but sometimes even of thirty-two ranks, the first five of which carried their pikes point-forward, and was subdivided into six battalions (taxeis), each of 1,500 men."
Alexander [the Great] then drew up his men until the phalanx was 120 ranks deep (1.6.1). Notice how the ranks varies greatly between 8 and 120!
Should we expect the phalangite's weaknesses to be any different than the hoplite's?
The answer is undramatic: no, the phalangite has the same weaknesses. Why? Because the only difference in its combat role amounts to the number of soldiers involved in the fight.
Phalangites are slow heavy infantry, probably slower than hoplites. But they engage the enemy at a slightly farther distance away, and are more effective against cavalry (if charged from the front!).
What other problems unique to phalangites could we imagine? Well, the equipment is heavier, so they probably tire quicker. This is bad: battles need to be shorter.
This also implies a dependence on skirmishers. If encountering missile fire, the phalangite cannot return fire. The only thing a phalangite could do is hope their shields or armor absorbs it.
So there is a dependency on skirmishers and light infantry to counter missile fire, and protect the flanks.
Remember that the intentional role Macedonian Phalangites play is crushing other heavy infantry. Indeed, compared to the Hoplites, the Phalangites seem quite capable of that job!
Next time, we will begin considering how to use Macedonian Phalanx in battle.