In 89 BC King Nicomedes IV of Bithynia and his large army marched along the Amnias River
across an open plain, invading the neighbouring Kingdom of Pontus. They noticed a small infantry
force of presumably Pontic soldiers securing the strategic position as they approached a hill. His
scouts informed him all there was ahead was a Pontic reconnaissance party, nothing his
soldiers would not be able to handle. Nicomedes was confident this would be a quick victory and
morale boost for his troops. He ordered his men forward. It should be an easy victory.
[Background]
Preceding the battle of the Amnias River, it is essential to understand the reign of one man in
particular. In 120 BC 15-year-old Mithridates ascended to the throne of the Hellenistic
Kingdom of Pontus. Early on, it already became clear he was focused on expanding his territory.
And he did not shy away from using any means necessary to achieve his goals.
But most of his neighbouring states were Roman client states. Any attack against them surely
would warrant a military response by the mighty Roman Republic. To the south lay the Kingdom of
Cappadocia, to the west the Kingdom of Bithynia, with Galatia and Paphlagonia as buffers. To his
east lay the Kingdom of Armenia, a wealthy Kingdom that was increasing in power. Still,
the Kingdom was easy to defend and difficult to invade, including the welcome buffer it provided
between Pontus and the predatory Parthian Empire. But to the southeast lay Armenia Minor,
a wealthy region that lay for the taking. So around 115 BC Mithridates marched a large army
into Armenia Minor. He asked its King to hand over the Kingdom did so without putting up any fight.
Having secured the southeastern border of his Kingdom, a bit of luck struck him. To the north,
the Greeks who had settled on current-day Crimea were threatened by Scythian invaders. Not being
able to withstand an invasion themselves, they wrote to Mithridates and asked for help. He
happily sent over an army. They decisively defeated the Scythians and subjugated local
tribes on the peninsula. Then they crossed the Azov Sea, marching into the Kingdom of Bosphorus.
Suffering its own internal turmoil, the King was all too happy to hand over his throne to Pontus.
Mithridates had not even ruled Pontus for a decade and had already expanded its territory
significantly. Following solidifying his positions in the north, Mithridates looked to the east.
Colchis laid north of the Kingdom of Armenia and Mithridates probably rightfully estimated
that if he did not capture the territory giving access to the Black Sea, Armenia certainly would.
Not much is known about the actual conquest or inheritance. What is known is that before
too long a Pontic governor saw to day-to-day business. Mithridates put the majority of the
eastern Black Sea Coast under Pontic control. In the years after, Mithridates appeared to be
successful in expanding in the west. He fought local tribes, and archaeological
findings indicate he controlled territories from Tyras to Mesembria. All these recently
conquered territories were allowed to retain their kings as long as they paid tribute to Pontus.
[Anatolian Affairs]
While consolidating his territories to the north, east and west, political turbulence
on Asia Minor remained part of his day-to-day life. The Cappadocian King Ariathes VI married
Mithidrates’ older sister, giving Mithridates ample opportunity to influence its politics.
But as time progressed and Pontus expanded, Rome too understood they had to tame the Kingdom. They
sent an envoy to Cappadocia and told Ariathes they would support a bid for complete independence.
It appears the King responded positively to these suggestions, and it is also clear news leaked to
Mithridates. In 116BC, Gordias, an assassin sent by Mithridates, assassinated Ariathes. His widow,
Mithridates’ sister, now continued the reign, formally acting as her underage son’s regent.
Rome would surely make known their discontent if Mithridates were to grant himself too much
liberty in annexing territories. However, Rome was encumbered with constant invasions
by barbarian tribes from the north and an incredibly unruly Numidian king, Jugurtha, who
went against Rome’s policies any chance he got. Mithridates had tasted victory, and he wanted
more. Together with King Nicomedes of Bithynia, they annexed the entirety of Paphlagonia. After
splitting it with Nicomedes, he invaded Galatia on his own, expanding his Kingdom further westward.
This action could not go unpunished… and it didn’t. Rome sent a delegation to Bithynia and
Pontus, demanding they return the territories and halt their expansionist ways. Mithridates
ensured the delegation he would.. The delegation left, satisfied, and Mithridates ignored their
every demand. Instead, as soon as they left, he helped himself to a larger portion of Galatia.
Meanwhile, Nicomedes, too tasted the success of going rogue. But to his west and south lay
actual Roman provinces, and the King understood he should not bite off more than he could chew.
So instead, he led his army on a daring march through Pontus-occupied Galatia into Cappadocia.
Mithridates’ sister, who was still upset her brother killed her husband,
eagerly married Nicomedes. Offended and insulted,
Mithridates sent a massive army across the border to expel the newlyweds.
He then reinstalled his nephew on the throne. But his nephew wasn’t planning on being his
uncle’s vassal. With Armenian financing, he raised his own army in record time.
Mithridates set up a meeting to resolve the conflict with diplomacy. At the meeting,
he killed his nephew, installing his own son on the Cappadocian throne with Gordias as his regent.
The region can be rightly described as a troublesome one. Around 99 BC Consul Marius
diverted his attention to the east again. The subsequent diplomatic mission to Pontus made
clear Mithridates should stop his antics and forced him to grant Cappadocia independence.
Instead, Mithridates began using proxies to exert his influence. For example, when in 94 BC
Nicomedes III passed away, Mithridates supported one of his bastards, Socrates, to seize the throne
and expel Nicomedes IV, the legitimate heir. He also goaded Armenian King Tigranes II to invade
Cappadocia and install Gordius on the throne once more. This gross violation was one step too
far for the Romans who considered themselves to have been very patient with Mithridates.
[Lucius Cornelius Sulla]
The Romans had just the man for the job. Lucius Cornelius Sulla made a name for
himself as an able military commander against King Jugurtha of Numidia. Around the time,
he was already on the way to Asia Minor to deal with a pirate problem on its southern coast.
Meanwhile, Mithridates continued building up his army and navy,
gaining naval supremacy and levying troops from conquered territories. Meanwhile,
Rome suffered from instability as the Social War broke out between Romans and Italian tribes.
As war waged on, Rome sent an envoy to Asia Minor to reinstall the kings of Cappadocia,
Bithynia and restore Paphlagonia. But the Roman envoy in Manius Aquillus also received the
specific task to immobilise the rogue Pontic King. Initially, Mithridates only received the orders to
reinstall the kings immediately. He understood he would not be able to face Rome’s military might.
But to his surprise, after reinstalling the Kings, Aquilus ordered the new Bithynian
and Cappodician kings to raid Pontus. Only Nicomedes, king of Bithynia and
heavily indebted to Rome, agreed to this near-suicide mission. In 90BC, he sent an
army into Pontus. Perhaps ironically, these raids were a fantastic propaganda tool for Mithridates.
Especially because Aquilus began openly organising an invasion of Pontus.
Rome didn’t have many legions stationed in Asia Minor. Sulla had to make do by raising
local auxiliary units. King Nicomedes, Cappadocia and the Galatians contributed many troops hoping
to increase their control in the region. The plan was to invade Pontus from the
south and west. On Pontus’ southern and western borders stood Roman commanders,
ready to invade. However, the first combat would not be between Mithridates and Roman commanders,
but between a Pontic reconnaissance party and King Nicomedes’ entire Bithynian army
in the north-western Pontic valleys. As part of the invasion, King Nicomedes
marched a large army into the highlands of Paphlagonia, marching through the valley
of the River Amnias. He planned to follow a well-known road leading into the Pontic heartland.
Then, if all went well, he would bend south and unite his army with the Romans.
But closeby danger loomed. Mithridates’ main force camped at Chiliokomon, current-day Asar.
Mithridates’ scouts stationed around the border informed the
military encampment a large Bithynian army was marching into Pontus. But they weren’t
sure if it was an actual invasion or another raid like earlier that year.
After sending another scouting party, the Pontic generals wrongly assumed it was just
a scouting party. A few of them took up the task to take care of the invaders.
[Aftermath]
This major victory was a great morale boost for Mithridates. He made sure to exploit its
propaganda value to the limit. However, he also understood he had a larger fight ahead of him.
As such, he offered the Bithynian mercenaries to join his army, as he explained to them his real
quarrel was with Rome. Following the Battle of Amnias, it is likely Mithridates welcomed
thousands of new mercenaries into his army, exceeding the losses suffered during the battle.
And Mithridates indeed had a larger fight ahead
of him. The First Mithridatic War had only just broken out.
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[Battle formations]
Together with his Armenian horsemen, Pontic General Arcathias set out to stop the Bithynians.
Generals Neoptolemus and Archelaus joined him. Together with the Armenian cavalry,
light infantry and several heavy scythed chariots, they moved north. Though numbers are unknown,
the army numbered around 10.000 Armenian cavalry and an unknown number of light infantry.
However, it was certainly only a fraction of the 250.000-strong main Pontic army.
Meanwhile, Nicomedes and his heavy infantry and cavalry slowly trekked south along the Amnias
River. Among his troops were approximately 50.000 infantry soldiers and 6000 cavalry.
The armies approached each other around several elevations
amidst the open plain they marched on. The Pontic generals ordered an infantry
contingent to seize the hills to secure a strategic advantage and defensive position.
But Nicomedes too, saw the rocky outcrop. He ordered his army to take their battle positions.
His front centre line was manned by his light infantry, peltasts. His flanks were manned by
his phalanx, while he himself commanded a cavalry unit. On the left, another
phalanx guarded the rear. Instead of a minor vanguard, he ordered his entire army forward.
The small Pontic unit was at risk of encirclement and fled upon seeing the approaching army.
[Battle sequence]
In response, Neoptolemus ordered his infantry forward while the Armenian cavalry protected
his right flank from the rear. Archelaus and his light infantry now swerved to the
left side to prevent the concentration of Bithynian force against Neoptolemus.
The centre of Pontus’ army charged into the centre of Bithynia’s heavy infantry.
Heavy close-combat fighting broke out. The Armenian cavalry charged into the
Bithynian frontline as well. The Bithynians inflicted heavy damage on the Pontic infantry,
and before too long, troops began crumbling. They would not be able to keep up this fight for long.
Archelaus and his light infantry now launched their attack into the Bithynian right flank. They
faced the Bithynian Phalanx positioned there and faced challenging and brutal close combat. But at
least they relieved the pressure from the centre. Neoptolemus ordered his army to retreat briefly
to regroup and prepare for the next charge. In contrast to his battered army, Arcathius’
cavalry had been packing a serious punch. He pulled back as well to regroup. Realising his
cavalry outmatched the Bithynians, he figured his cavalry was better used outmanoeuvring the larger,
immobile army rather than charging into the frontlines. He now tried to look for an opening
on his right flank to circumvent the Bithynians and encircle them. The hill provided welcome cover
for his maneuvring. To distract the enemy, even more, he ordered the heavy chariots to launch
an attack against the Bithynian left flank. Roman historian Appian described the scene:
The chariots “were driven at high speed into the Bithynian ranks. Some men were
sliced in two within an eyeblink, others were practically shredded.
The army of Nicomedes saw men in two halves, yet still alive and
breathing, others sliced to pieces, their mangled organs still hanging
from the scythes. They had by no means lost the battle, yet the sight
was so hideous that they were overcome
with confusion, and fear disordered their ranks.”
Upon seeing the onslaught, Neoptolemus charged into the Bithynian infantry again. Because their
phalanx was fighting on two fronts, parts of their lines slowly began opening up,
and their army formation became disorganised: a grave danger for a phalanx.
Then, suddenly, the Bithynians suffered an even worse blow. Arcathius managed to
traverse around the hill and unexpectedly turned up behind the entire Bithynian army.
Pontus had the Bithynians in a pincer movement. With a loud rallying cry,
the Armenians charged into the rear of the phalanx guarding the left flank. Encircled
and with no way to escape, the Bithynians continued the brutal fight, albeit briefly.
Nicomedes understood that even if he could turn the fight,
he was only facing a reconnaissance party of the Pontic army. The main army was not even there yet.
As such, he fled from the battlefield. According to Appian, he did not order his troops to retreat.
Instead, they took their king running as a strong indication they should as well.
Those who weren’t able to escape were captured. But Mithridates didn’t plan on executing them.