The great Corinthian victory at Eleusis during the First Syracusan War, had secured the Athenian/Corinthian dominance over Greece and Sicily. However, the Corinthian victory was overshadowed by the vast colonial expansion of the Delian League, which now controlled half of Sicily and the Crimea. For nearly 30 years, Athenian wealth and trade with Corinth brought the peninsula to new heights, along with the foundation of a trading league known as the Peloponnesian League. The League consisted of the remaining independent states in the Peloponnese, and was created to make a more balance system of trade with Athens, who openly encouraged the new foundation. However, vast Athenian monopolies and dominance at sea, began to usher in exotic items from Egypt, Persia, and in some cases, the far east. These luxury items were unmatched in price, and Corinthian merchants began to buckle under the weight of the expensive wares. Soon enough, Athens stockpiles of lavish products completely dismantled the effectiveness of the Peloponnesian League, whose even finest items quickly became worthless. Athenian wares were soon only sold to the riches of the richest, the Persian Empire, who made Athens extremely wealthy.Soon enough, Corinth perceived itself to be neglected by its Athenian allies, and looked west for trade partners. The rising powers, such as Rome, gave Corinth a brief relapse in wealth, but quickly the trade disintegrated. Finally, in the 370s BCE, Corinth and its allies entered an economic depression state. Soon enough, over the desperate need for gold, several small wars erupted in the peninsula. Smaller cities were gobbled up by cities such as Corinth and Argos, who taxed their populations without second thought. Eventually, the wars divided up the Peloponnese into seven spheres of power; Corinth, Argos, Elis, Megalopolis, Messene, Geraki, and Patra.
Initially there were six spheres in the Peloponnesin, with Laconia still divided between the marauding Helot armies following the Great Helot Revolt. Finally, after 369 BCE, the Helot city of Geraki successfully subdued a series of neighboring cities, and made peace with the remains of the Lacadonian states.
With the seventh power in the Peloponnesian Secure, the three powers convened to initiate the reformation of the League from a trading system, to a military alliance. The League then raised a substantial fleet, and captured a series of disputed regions in the southern Aegean, provoking a degree of Athenian hostility.
As Delian rebellions became more and more frequent in the growing Delian League, due to a increasing lack of independence by Athenian "client" states in the Aegean, the Peloponnesian League prepared to strike at the increasingly weakening league. In 363 BCE, the Athenian Assembly voted to adjust taxes on Athenian client states in the League, prompting another rebellion in Anatolia. Timotheus was drawn away to deal with the issue, leaving Helmetrus with a smaller force behind. In January of 362 BCE, the League voted in its next two leaders, or their de facto title; King. The kings were almost entirely dominated by Corinthians and Messenians, and had been so since the Leagues foundation. Due to the circumstances, the assembly of the league elected two staunch conservatives, Atimorachus of Corinth and Igleusis of Messena, for a five year term of absolute power. Atimorachus and Igelusis were swift to act against Athens, and seized the Isthmus of Corinth which had been in Athenian possession since the Peloponesian War (or the Second Peloponnesian War).
The invasion of the Isthmus of Corinth was a surprise to the Athenians, who had neglected the Corinthian rise to power. The true beauty of the invasion was not the abrupt action of the Corinthians, but rather their ability to combine naval and land forces to effectively invade a small width of land. With extensive preparations, the Corinthian Navy was able to shuttle troops across areas of defense. The Athenian Navy, rushed to defeat the smaller Corinthian naval unit near the Isthmus, but was caught in a small group of islands, where the Corinthians encircled them at the Battle of Argolikos Koilpos.
With half of the Athenian Navy destroyed and the city herself under a naval blockade, the Athenians scrambled for a solution. Despite the fact that Athens could withstand the blockade because of her vast land trade across the Delian League, the invading Peloponnesian Force posed a threat that could forever dismantle the Athenian Hegemony. The Assembly turned to Helmetrus, and convened a vote to give the young general total command of the Athenian Armies. The Espistates, the executive power in Athens, was abruptly swayed into support of the new legislation and turned to the courts to confirm is legality. Helmetrus, who was simply one of the 10 Athenian Generals, persuaded the courts that if the Assembly elected him to the position, then the act was just. The courts agreed, and the suggestion was brought up to the Assembly. Despite heavy opposition of the bill, Helmetrus's supporters won out, and the the young champion was named Πρώτη Γενική (First General). These new powers allowed Helmetrus to carry out military actions without the consent of the Assembly, which Helmetrus argued would limit delays in warfare and allow the military to achieve decisive victories.
The First General marched out of Athens on the day of his political victory, and took command of the armies of Attica, which numbered 30,000 men, the largest united army in all of Greece. At the same time though, the Peloponesian League had deployed its entire force, which in a combined force outnumbered the Athenians by a slim quantity. However, the allied armies were far from united, and it was clear that the Corinthians would have to move quickly in order to solidify the alliance.
Helmetrus divided his army into three armies, two of them numbering 14,000 and the latter numbering 2,000. Helmetrus desired to make the appearance of two armies, while using his elite troops in the third to swing the tide. King Atimorachus of Corinth and his co-ruler, decided to divide their own armies into two, copying their enemy in a effort to avoid a flanking maneuver. The two rulers were convinced that the Isthmus was too thin for any grand maneuvers, and decided that Helmetrus had to seek open conflict, in which the terrain would be in the Corinthians favor.
Helmetrus moved one of his armies to the Northern section of the Isthmus, drawing in one of the Corinthian armies. The second Corinthian army, under Igleusis, was unable to reinforce Atimorachus's troops, as the southern Athenian army had engaged the Corinthians in a series of skirmishes.
In the meantime, Helmetrus had his third army march up the center of the Isthmus and take position near a small heavily forested area. The Northern Athenian army then followed up by forcing Atimorachus into a better supplied position, which happened to be near the Third Army. Helmetrus engaged and defeated Atimorachus by outflanking the Peloponnesian forced with his Third Army while his Second Army openly engaged the Corinthians, at the Battle of Perachora. The Peloponnesian Forces were forced to withdraw south away from the Perachora region in a merging move with Igleusis's army.