This was supposed to be a response to a top response, but that got deleted, so I'll just start a new thread.

While it was certainly true that the Roman Maniple system was more flexible than the Hellenistic phalanx, I hesitate to give it the credit that it played a major role. Not to say that it didn't play a role at all, but just not as big as many would want it to be.

(EDIT: this paragraph was a rebuttal against the guy I was referring to, but is largely irrelevant now, but I'll keep it in case anyone had this idea) First, I should note the less important distinction that the Hellenistic phalanx usually did not have large enough shields to overlap. The Greek hoplite did, as their shield was about 3 ft in diameter. The phalangite shield varied much more widely, sometimes being as small as a buckler. Indeed, the "pushing" power of the Macedonian phalanx was the pikes, not the shield. I know of no sources that state the effectiveness of the Pila against the phalangite shield in any battles.

The fact that Macedonian/Diadochi phalanx was less maneuverable in itself does not necessarily imply that it was inferior to the Roman infantry, as the phalanx was designed to have adequate light infantry and cavalry support at its flanks anyway. Alexander's army was very much a combined-arms army, and the Diadochi states also understood the importance of non-phalangite heavy and light infantry. The Seleukids adopted the originally Gallic design of the thorax, the Ptolemaics heavily utilized local Machimoi troops, and every other Diadochi state followed the pattern of utilizing local fighting style troops. Thus, the major vulnerability of the phalanx was supposed to be more than offset by the plentiful supporting troops flanking them.

Case in point, if we look at the battle of Heraclea with Pyrrhus of Epirus (not the Pyrrhic victory one), the battle was stalemate for allegedly 7 attacks from each side, and was only broken by the elephant charge at the flanks. In Pydna, the Romans initially struggled greatly against the front of the phalanx, and the tide mainly turned due to the uneven terrain during the Macedonian push that left gaps in their lines that the more flexible Romans capitalized on. In Cynoscephalae, the stalemate was broken by the elephant charge at the phalangites, and the Roman infantry followed up at the gaps. These are 3 of the most famous battles between Maniple and Phalanx, yet they were all caused by non-infantry factors that the Roman infantry excellently utilized to their advantage. This is good evidence of the high level of training and autonomy of the Romany infantry, but this pattern of exploiting the gaps is not unique to the Romans, I'd argue that this would have been no different if conducted by a non-Roman heavy infantry element that was equally well-trained.

Interestingly enough, if we stop focusing on the Romans for a moment, we see that the Diadochi states eventually phased out the phalanx by themselves anyway. The phalanx numbers shrank as time went on, and by the time Rome fought the Ptolemaic kingdom at 48BC, phalanxes were not mentioned at all (though it was admittedly a siege).

However, I hesitate to make this as evidence that the phalanx became technologically outdated troops, as by the Renaissance era, we see a resurgence in pike and polearm formations that highly resembles the Macedonian phalanx. These pike formations stayed on the battlefield until the late 17th century. That's longer than the reign of the Macedonian phalanx! Thus, we know that tightly packed men with long pointy things work, and worked well until gunpowder finally overthrew their dominance.

Then why did the phalanx hibernate for over 1000 years? I think it's likely because of the high degree of organization and training required to deploy a phalanx correctly, and the economic incapacity of the states to do so. As I've stated, phalanxes require lots of combined-arms support, and the Seleukids and Ptolemaics were just too big and corrupt to to be able to field well-trained, competent armies like Alexander's. The Gallic and Germanic tribes were not experts of military science with unified troop types, the Hispanics had too many hills and forests, the more Eastern and steppe tribes relied on the bow, and the Carthaginians's military doctrine was to rely on mercenaries (NOTE: these are all generalizations, and there were many exceptions to the rule). After the decline of the Roman empires, it took quite a while before armies were as big and organized as those of 200 BC. Kingdoms were much smaller, military logistics was basically non-existent, and troops did not go through such organized reforms as the Hellenistic and Roman states did for hundreds of years.

Thus, if I had to point the finger, I wouldn't point it to the troop types or the tactics. I'd point it to the rulers, governmental efficiency, and economic management of the times.

Sources:

Goldsworthy, A. K. "The Othismos, Myths and Heresies: The Nature of Hoplite Battle." War in History (1997): 1-26.

Hanson, Victor Davis. Hoplites the Classical Greek Battle Experience. London: Routledge, 1993.

Livius, T. (n.d.). Ab Urbe Condita Libri (Vol. VIII).

Livius, T. (n.d.). Ab Urbe Condita Libri (Vol. XIII).

Plutarch, Mensch, P., Romm, J., & Beard, M. (2017). The age of Caesar (1st ed.). W. W. Norton & Company.

Shipley, G., & Rich, J. (1995). War and Society in the Roman World (1st ed.). Routledge.

Warry, J. (2000). Warfare in the classical world. New York: Barnes & Noble.

Related question: out of curiosity, how effective were the pila and ballistae against phalanx-based forces when compared to the more mobile and en masse tactics of the Celts, Germans and Carthaginians?

It seems to be that the more innovative of military tactics/tools that the Romans had were best suited against phalanx-based forces. What sort of contrasting weapons or tactics did they employ (if any) when they faced more mobile berserkers?

Edit: (I've always wondered about the future shields of the vikings... they are light with iron rims and they seemed to carry additional shields... could this have been started in order to throw a shield that has been stuck with a pilum only to grab a fresh one?)

Firstly, this question is very big in scope and can't be answered succinctly. You're attempting to generalize an array of empires, kingdoms, and poleis across hundreds of years into one single explanation for why the Romans were the ones "left standing." There is no such answer. Of just the three kingdoms you mentioned, there are a dozen or more wars that would be involved in this answer, each involving very distinct social, political, and economic circumstances that led to those events and influenced their outcomes. Each war is a historical field of study of its own.

I can attempt to answer this broad question for specifically Pontus in the context of the three Mithridatic Wars but there are many unknowns and scholarly disagreements so there is no conclusive answer in this instance either.

One last caveat before I get into the meat of this answer, drawing relation between the Diadochi/Successor kingdoms and Pontus is very dubious. Pontus broke away from the Seleucids in the early 3rd century BCE and the Mithridatid dynastic line has no recorded relation to the Diadochi of Alexander. Of course, there was Hellenistic influence on their culture and they came to eventually occupy Greek coastal poleis, however, there is much debate as to how much the Hellenistic culture penetrated aristocratic and civilian culture in Pontus. During its height under Mithridates VI, he was said to speak upwards of 24 languages, all of which were spoken by his subjects, and the cultural area ranged from steppe tribes north of the Caucasus to Celtic peoples in Anatolian heartland and to Persian influenced areas along the Armenian border. There are few signs of any hegemonically imposed culture upon this vastly diverse groups of people which is largely the argument championed by Christian Marek and other scholars that there is not real “Pontic identity.” It was a confluence of Persian/Zoroastrian, Hellenistic, and native Anatolian traditions that made for social make-up of each city with a monarchic system projected on top of these local governing bodies. I mention all of this to try and illustrate the different cultural background a Pontic “levy/soldier/militia” would have compared to a given Roman legionnaire and thus how this could be both advantageous and disadvantageous to Mithridates VI.

For more background into this war, see my other post detailing the political narrative leading to the Asiatic/Ephesian Vespers.

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As I said in my previous post and will reiterate here, the Mithridatic Wars are woefully overlooked in the pop-history political narrative of Rome. Often times, they are simply a hiccup for Sulla to deal with while Marius consolidates power in Rome. Occasionally some authors will dig a bit deeper you’ll get brief descriptions of sweeping victories at Chaeronea, Orchomenus, and Tigranocerta and then Pompey shows up and his magnanimous presence simply ends the war. And part of this is not to blame of scholars that have shaped the mainstream discourse of Late Republic Roman history, as there is likely a deliberate effort by Roman/Greek authors themselves to whitewash some unflattering aspects of the wars. Though epitomized from a lost source, there are scant details about Pontic victories at Chalcedon, Zela, and the Battle of Halys, as the only set piece battle of the Second Mithridatic War is sometimes called. From my Horace White translation of Appian, the author spends entire books on the Siege of Athens and Piraeus, however, for the loss Murena suffered on the banks of the Halys, Appian has only this to say:

“Gordius straightway seized and carried off a large number of yoke-animals, beasts of burden, and men, both private citizens and soldiers, and took position against Murena himself, with [the Halys River] flowing between them. Neither of them began the fight until Mithridates came up with a large army, when a severe engagement immediately took place on the banks of the river, Mithridates prevailed and crossed the river, and in all respects got the better of Murena. The latter retreated to a strong hill where the king attacked him. After losing many men Murena fled over the mountains to Phrygia by a pathless route, severely harassed by the missiles of the enemy.”

There are many reasons why this battle would not have many details recorded but it is easy to suspect that Romans likely didn’t enjoy talking about their defeats much. This bias is important to note in the context of these wars because it is, in the opinion of other scholars and myself, manifested in much of the information we have about these battles and wars, the biggest area of suspect being the HUGE number of soldiers Mithridates (and Tigranes) was purported to muster which I feel are inflated. The reasoning why I feel that is for another discussion, so I won’t get into that.

cont...

A bit late to the party but I'll showcase my view on the macedonian phalanx vs maniple question.

To begin with, the Macedonian style army went through some significant changes from the time of Alexander to the time of the later Successor Kingdom states.

I think examining Alexander's phalanx is essential. Alexander's phalangites used a slightly shorter and lighter pike, and they were most times supported by light infantry (archers, thracian peltasts and agrianian peltasts) on the sides, along with the hypaspists who were supposed to be more flexible (either equipped in the form of heavy hoplites, using an aspis, or they would deploy with lighter equipment when required), in several of Alexander's battles he also placed allied infantry (hoplites), behind the main line or to secure the camp.

Following Alexander's death, the infighting between his successors heavily depleted the numbers of pure Macedonian/ Greek soldiers available, and especially in Macedonia, since lots of the able-bodied men(potential soldiers) would leave to go and serve as klerouchoi in Egypt or under the Seleucid kings in military settlements.

Unlike what most people think the Macedonian Phalanx did not fight in a solid/ inflexible line. Each unit, under its commander, fought as an independent combat group. Alexander's 'oblique order' formation at Gaugamela proves this, where his right wing advanced towards the Persian left. It would be impossible for a solid, rigid line of pikes to advance at an angle. The battle of Sellasia and Asculum proves this also, where Pyrrhus used Tarantine, Allied Italian levies in between his pike formation, as well as the battle of Magnesia where Antiochus divided his phalanx in 10 divisions and placed 32 elephants between each contigent (big mistake, but we'll talk about it later on).

Another debate is whether the Macedonian phalanx was inherently inflexible. In my opinion, the phalanx was not as inflexible as most people believe. In many circumstances the pikemen were able to perform complex maneuvers and fight on uneven terrain. Examples of this is the battle of Chaeronea, where the Macedonian pikemen retreated in good order and 'individual units were positioned where the situation required’.¹ In Thebes Alexander divided his army into three separate groups (including pikemen), to attack the palisade which had been erected in front of the city, and ordered on unit of pikes to be held in reserve behind the main battle line and advance where the soldiers became hard-pressed by the Thebans.

Appian also describes how the pike-phalanx of Antiochus at Thermopylae opened its files to allow skirmishers to withdraw, the formation then reformed into an intermediate order and, once in position, lowered their pikes for battle.

Another maneuver that the successor pikemen used was that of the defensive square, a very difficult one to pull off, but it was done in several circumstances, such as the battle of Gabiene 316 BC and Magnesia 190BC.

The Phalanx Fighting on uneven terrain- the main evidence of the phalanx not being able to fight on uneven terrain comes from Polybius (2nd cent. BC). Where he claims that " The phalanx…requires ground that is level and bare which has no obstacles " (I think Plutarch mentions this too), but he also uses the word flat (epipedos) to describe lots of places that are not flat at all (Leontini, Sellasia). The Macedonian phalanx fought numerous battles on uneven terrain such as Chaeronea, Sellasia, Antiochus campaign in Parthia, Jaxartes etc. and were victorious.

Now let's look at some battles more in depth.

BATTLE OF CYNOSCEPHALAE

The battle of Cynoscephalae was the main major battle between the Romans and the Antigonid Macedonians that decided the 2nd Macedonian War. The battle was fought on high and uneven ground and it was described as 'rough, precipitous' by Polybius.

Following a skirmish between the two forces, a full-on battle ensued, with Philip V advancing only his right-wing of the phalanx on the ridge. The phalanx units on the Macedonian right wing effectively engaged the Romans and pushed them down, however the Macedonian left is what won the Romans the battle. According to Livy, the left-wing was brought up the ridge in a column rather than an extended line (which is weird since a column is usually used in marching) and some of the soldiers deployed and were fighting while others had just reached the top of the hill