Dion in Harpers Dictionary of Classical Antiquities (1898)
An inhabitant of Syracuse, who became a disciple of Plato, invited to the court of Syracuse by the elder Dionysius. He was nearly connected with Dionysius by having married his daughter, and because his sister was one of his wives; and he was also much esteemed by him, so as to be employed on several embassies. At the accession of the younger Dionysius, Plato was again, at Dion's request, invited to Syracuse. (See Plato.) In order, however, to counteract his influence, the courtiers obtained the recall of Philistus, a man notorious for his adherence to arbitrary principles. This faction determined to supplant Dion, and availed themselves of a real or supposititious letter to fix on him the charge of treason. Dion, precluded from defence, was transported to Italy, and from thence proceeded to Greece, where he was received with great honour. Dionysius became jealous of his popularity in Greece, especially at Athens, stopped his remittances, confiscated his estates, and compelled his wife, who had been left at Syracuse as an hostage, to marry another person. Dion, incensed at this treatment, determined to expel the tyrant. Plato resisted his intentions; but, encouraged by other friends, he assembled a body of troops, and with a small force sailed to Sicily, took advantage of the absence of Dionysius in Italy, and freed the people from his control. Dionysius returned; but, after some conflicts, was compelled to escape to Italy. The austere and philosophic manners of Dion, however, soon lost him the favour of his countrymen, and he was supplanted by Heraclides, a Syracusan exile, and obliged to make his retreat to Leontini. He afterwards regained the ascendency and caused Heraclides to be assassinated, which robbed him ever after of his peace of mind. An Athenian, an intimate friend, formed a conspiracy against his life, and Dion was assassinated in the fifty-fifth year of his age, B.C. 354 (Diod. Sic. xvi. 6 foll.; Dion.; Corn. Nep. Dion).
Dion of Syracuse in Wikipedia
Dion (Δίων 408–354 BC), tyrant of Syracuse in Sicily, was the son of Hipparinus, and brother-in-law of Dionysius I of Syracuse.
Dion was the son of the Syracusan statesman Hipparinus, who had assisted the despot Dionysius I, in the Syracusan army. Hipparinus' other children were Megacles and Aristomache. Aristomache married the despot Dionysius I, who married the Locrian Doris simultaneously. Although Dion's sister was beloved by her fellow Syracusans, it was Doris who gave birth to the heir (Dionysius II). Aristomache had four children. Among them, Sophrosyne married the younger Dionysius, and Arete married Dion (whose son was Hipparinus). 
Dionysius the Elder's closest adviser
Dion was so close to the elder despot that he was given the most important assignments. Dion excelled in managing the embassies that dealt with the warring Carthage. The despot was satisfied with Dion's adviser role so, eventually, Dion was authorized to withdraw money from the realm's treasury. The despot demanded, however, to be informed daily when he did so. Dion thereby became extremely rich and his residence was magnificently furnished. Nonetheless, Dion occasionally criticized the despot. 
The arrival of Plato
From his youth, Dion had excelled in intellectual activities. He convinced Dionyius to invite Plato (who was visiting the Italian peninsula) to Syracuse. Dion joined Plato's philosophical school, excelling amongst his other disciples.
Dion used every effort to inculcate the maxims of his master in the mind of the tyrant. Once, Dion invited the despot to a conference with Plato. However, Dionysius was offended by the philosopher (who was speaking against tyrannical leaders, in general). This ensued in a quarrel, after which the despot ordered the assassination of the philosopher (who ended up sold as an Athenian slave, at Aegina). Nonetheless, between Dion and the despot, the relationship continued as before.
Succession to Dionysius
Dionysius was on his deathbed when Dion attempted to discuss the succession (on his Syracusan sister's behalf) with him. The attempt was intercepted by the doctors (who tried to ingratiate themselves with the younger Dionysius, who was the natural heir). He then deliberately poisoned his father, who was unable to utter another word, before passing away.
Dionysius the Younger
The elder despot had dreaded that anyone might depose him treacherously. He had therefore cloistered his own heir so he grew up inside the Syracusan acropolis, neither acquiring the minimal formation nor developing any personal fibre. Besides, the younger Dionysius was given to libertine practices. Furthermore, when he succeeded, his entire court was formed by licentious youngsters, who were completely disengaged from their political duties. The Syracusan institutions thus began to collapse. Instead, with both his large experience and his moderate life, Dion was the same correct functionary. Soon, the people deemed that he was the only one who might save Sicily. In the court, Dion proposed the Carthaginian war. Dion offered either to travel to northern Africa (to end the situation diplomatically) or to furnish Sicily with 50 new triremes (for war) with his own money. Although Dionysius the Younger was delighted by this, his courtiers began resenting Dion's interventions (who didn't join their revelry). Particularly, (jealously) they suggested to Dionysius that Dion was trying to oust him, in favour of the line of his sister Aristomache.
Dion concluded that educating Dionysius would be the resolution to all Syracuse's problems. With his philosophical base, Dion began teaching him about the most basic politeness and, soon, he began talking about more tolerant forms of government. Such lessons sparked the ruler's desire so Plato was invited again to Syracuse. However, the opponents gained influence with Dionysius, so the tyrannical philosopher Philistus was recalled (after he had been banished, by the elder Dionysius), and founded his own political party immediately.
Under such circumstances, Dion began building a conspiracy, with both Heracleides and Theodotes. They would wait patiently for political reform, although they would oust the despot if this may not happen. Eventually Dion was ready to install a full democracy, although, by his wealthy patrician birth, he disliked this type of government.
Nonetheless, Plato arrived and he was welcomed with much éclat. Effectively, this meant significant changes in Dionysius, who became sober and attentive, whereas his realm lived an intellectual fad. Then, during a traditional sacrifice, the ruler (who was so civilized, now) declaimed openly that he didn't want anymore, to be a despot.
Such an event alarmed the partisans of Philustus, and they campaigned intensively against Dion. To Dionysius, they insisted that (slighting the military power and the magnificent treasures) the ruler was chasing pathetic chimeras whereas Dion was the greatest deceiver, who expected (meanwhile) seizing the entire realm for his own nephews. Dionysius began believing such reasons so the despot adopted a hostile attitude, toward Dion.
The situation peaked when Dionysius and Philistus intercepted an obscure letter, which had been sent by Dion to the Carthaginians. Dion recommended that they should consult him, for a peace agreement, because he would provide all demands to them. Fearing an international plot of Dion, the resolute despot feigned a sudden friendship then and, with him, Dion walked to the seashore (which was under the Syracusan acropolis). There, the despot showed the letter to Dion (who wasn't allowed to argue) and, immediately, Dion was forced, sailing toward the Italian peninsula. Diplomatically, Plato was confined inside the acropolis (receiving excellent treatment, as an important guest) thus he wouldn't follow Dion (divulging such events, amongst the Athenians). When the Carthaginian war restarted, the despot allowed the philosopher's departure too, promising the return of Dion for the next summer.
By such events, it was probable that, with her princely children, the more popular Aristomache (who was preferred, as Syracusan, by her fellow citizens) would seize the power. Even, the people wanted this (expecting some sort of break, off the 50 years old despotic regime). Dionysius noticed this and he attempted, amending the situation. Publicly, he explained that (for his own sake) Dion was temporarily at Athens so (with his current obstinance) he wouldn't provoke some violent backlash of the despot. Still, Dion held his Syracusan estate and he was receiving the usual revenues of his businesses as well. Furthermore, the despot handed two vessels, to his female relatives, so they could send his rich possessions behind him, to Athens. Besides, the women added many rich presents.
Thus, Dion lived amongst the Athenian high society, dwelling at the upper Athens with the patrician Athenian Callipus (who would be his murderer, eventually), with whom he had gotten acquainted during the celebrations of the Eleusian Mysteries. Additionally, Dion purchased a rural residence, for leisure. His closest friend was the mirthful Speusippus (with whom he spent most time).
However, the young despot protracted the return of Dion, now until the end of the war. Underhand, he recommended Plato that Dion shouldn't declaim publicly, against the Syracusan regime. Consequently, Dion obeyed, staying within the Athenian Academy, studying philosophy.
However, Dion began traveling throughout the region (transgressing the requested low profile), meeting many local statesmen. Indeed, Dion was quite celebrated by his personality (which was so courteous and intellectual) and many Greek urban centers rewarded him. For instance, the Spartans endowed him with the local citizenship, although this nation was warring against Thebes and being allied with Dionysius (who enraged, by such news).
Eventually, the jealous despot decided, seizing all Dion's Syracusan properties (through his royal chamberlains), sending his revenues no more. Also, the ruler expected mending his international image, forcing a new visit of Plato, through public threats against Dion. Effectively, the celebrated philosopher returned to Syracuse though, after some hypocritical cordiality, they began arguing bitterly, about Dion's wicked fate. The philosopher ended jailed, amongst the royal soldiers (who were desirous to kill him, indeed), until an Athenian embassy released him. In his consequent rage, Dionysus sold Dion's estate (plundering the money) and Dion's wife Arete was given, to the close adviser Timocrates.
Thus, Dion desired revolting Syracuse earnestly. Particularly, his closest friends were telling to him that, at Syracuse, the people were expecting enthusiastically, to revolt with Dion, if only he may get thither. Even, Dion should need to bring neither weapons nor soldiers.
Although (abroad) the exiled Syracusan leaders were quite scared (and few joined the expedition), Dion could gather many other important Greek figures. Eventually, they mustered 800 fine soldiers (who were ideal, to embolden the Syracusans properly), at Zacynthus. To these mercenaries, Dion assured that they would be Sicilian commanders once they may defeat the politically weak despot. At Zacynthus, Dion sacrificed to Apollo and, at the local racetrack, he served a magnificent farewell dinner with golden tableware and superb dishes, for the whole expedition.
In 357 BC, Dion's fleet comprised 2 merchantmen (which brought the soldiers), 1 ancillary vessel, and 2 triremes. Particularly, he loaded much food for they would sail through high sea (as the aware Philistus was surveying the Italian coast). After 13 days, they reached Sicily, at Pachynus. However (despite his own helmsman's advice) Dion ordered, sailing further along the southern coast of Sicily. Then, by some seasonal northern winds (which were followed by an intense storm), the vessels were pushed southward and almost they are crushed apart, against the rocky insular territories of Cercina, at northern Africa. The fleet had to wait for five days until a favorable southerly brought it back to Sicily. There, Dion had to land in Carthaginian territory. Although he was personal friend to the governor Synalus of Minoa, he hadn't recognized him, barring the disembarkment. Thus, Dion had to launch amphibious assault, ordering no slaying though. After both leaders met, the Carthaginian offered plentiful supplies, lodging the expedition of Dion.
Then, Dion's soldiers learned that Dionysius was visiting Caulonia (at the Italian Peninsula), with 80 ships. They insisted to Dion so they began their march, toward Syracuse. On the road, they were joined, by 5,000 other Sicilians (through Agrigento, Gela, Camarinea, and the rural Syracuse). Such people were wretchedly armed yet they were quite decided. Within the urban center, the Syracusans were emotionally stirred although they kept their calm, fearing the despot's informers. About Acrae, Dion spread the fake rumor that, beforehand, he would attack both Lentini and Campania. These regiments deserted Timocrates' forces, to defend their respective towns. Then, during the night, Dion ordered and the expedition advanced, reaching the Anapus river (which was 2 km from Syracuse). At the daybreak, Dion sacrificed religiously, in behalf of the rising sun. He had a garland on his head and the soldiers imitated him, crowning their heads with wreaths. After the gods granted victory promises, Dion launched the attack.
Before the arrival of Dion, the people slew all despot's agents and Timocrates (who couldn't reach the acropolis in time) had to flee. Dion led his army into Syracuse, through the gate of Temenitid. He wore a brilliant armor and a garland crowned his head. Beside Dion, Megacles and Callipus were while the foreign mercenaries led the large insurgent army. The local statesmen were awaiting for them, wearing white robes. After ordering a trumpeting, Dion proclaimed that both him and Megacles had deposed the despot. Then, Dion walked through the Achradina and the people threw flowers at him, celebrated with wine, and performed sacrifices. Dion climbed onto the magnificent sundial (which had been erected by the despots), on which he incited the citizens for their liberty. Reciprocally, by the people, Dion and Megacles were named full power generals and, together, both designated 20 syracusan generals (of whom 10 were formerly exiled figures).
A week afterward, the young despot filtered into his still-loyal syracusan acropolis (which hadn't been captured, yet, and which was holding its large garrison), with the protection of his loyal fleet, whereas Dion had built a palisade (which surrounded this fortification). Dionysus attempted negotiating with Dion but he responded that the now free Syracusans should decide. The proposals of the despot were utterly spurned and Dion suggested his surrender. Deceivingly, Dionysus accepted this and he invited a local embassy, to discuss the details. Dion picked the representatives, who were confined immediately after entering into the palace. After the daybreak, from the fortification, a surprising sally of the despot's army overwhelmed the many besieging Syracusans, who retreated in utter disorder. With his men, amidst such extreme confusion, Dion was unable to issue orders so he charged personally against the worst sector and (effectively) all his men followed him. However, the enemies recognized him, charging preferentially against. Dion was injured in his hand, his breastplate was completely beaten up, and his shield was pierced by many spears and javelins. Dion ended onto the ground and he was snatched out of the field, by his men. After Timonides took the command, Dion mounted a horse and he reunited all revolutionary forces, throughout Syracuse. Particularly, the great foreign mercenaries had superior skills, with respect to the frustrated despot's men (who had expected capturing Syracuse swiftly), who ended retreating back into the castle. By such signal victory, the Syracusans awarded 100 minae to the foreign men and Dion was presented with a golden crown, by his foreign warriors.
Losing popular stand
After some time, a package (which contained many personal letters) came out of the acropolis, onto Dion's hands, and he ordered their public reading. 2 letters had been written by Dion's female relatives (who begged for many things). However, other letter was inked (nominally) by the son of Dion although it was a Dionysius' missive (indeed). Nonetheless, it was read before the people, too. After some menaces, the despot reminded Dion's important past services (in the despots' behalf) and the letter ended recommending that Dion should enthrone a new tyrannical regime, to dodge the vengeful Syracusans (who may attack him, distrustfully).
Effectively, the people began distrusting Dion (whose political initiatives were conservative, already). Particularly, those Syracusans who were dedicated to liberal activities (such as the merchants) resorted to Heracleides, who was a famous officer, who had been exiled too. Enthusiastically, Heracleides learned the situation immediately and he formed his own political party. Then, he was appointed Admiral, by the assembly, so he gained the favor of the sailors as well (in the eminently maritime Syracuse). This enraged Dion, who demanded his destitution, because this would limit his full power command. Reluctantly, the people obeyed. However, both political leaders met at Dion's home and, to confront the despot unitedly (in such perilous days), Dion ordered the assembly and Heracleides was reinstalled in the admiralty.
Hypocritically, Heracleides had many goodwill gestures to Dion but (underhand) he kept instigating the Syracusans, for the most revolutionary causes. Furthermore, this popular leader's fleet was the one which fought the rest of the sicilian revolution and, in a battle, they captured Philistus (who was slain humiliatingly, before all Syracusans). The rivalry peaked after Heracleides couldn't prevent Dionysius' escape, through his blockade. (The despot's son Apollocrates was left, commanding the fortification) The Syracusans started rebuking the popular leader so (angrily) Heracleides decided sending Hippo and, together, to the popular assembly, they proposed so:
* the Syracusan land should be equally redistributed, amongst the citizens
* the foreign officers should lose their salary
* new commanders should be appointed
Dion opposed such plans and, then, the Syracusans reacted decisively, against his rather oppressive government (which relied much, on the so unpopular foreigners) thus 25 new generals (among whom Heracleides was) where appointed.
Confronting the Syracusans
Indeed, the foreign mercenaries had been offered, underhand, to receive full citizenship, if they might desert Dion. Nonetheless, they refused. Then, (with their leader) the expedition decided abandoning the ungrateful Syracuse. On that day, the soldiers rounded Dion protectively, against the aggressive civilians (who were about attacking them). Dion ordered that (without aggressing) their weapons had to be brandished and they escaped swiftly, with loud cries. The scared pedestrians retreated however, on their horses, some generals followed them, to a nearby river. There, Dion was really angry and his men formed, for an onset. Before this, the Syracusans fled, suffering some casualties.
At Lentini, Dion was friendly received whereas the foreign mercenaries were made local citizens. There, the Sicilian congress held a meeting, denouncing Syracuse, but they responded that they preferred their actual liberties, instead of other totalistic government (referring Dion).
At Syracuse, the navy had defeated a cargo convoy, which was destined to the Acropolis, capturing some ships. This ensued in a boisterous celebration of alcohol, which involved all citizens, throughout the streets. Before such extreme unrestraint, Nypsius (who had commanded the vessels) ordered an unexpected sally and his soldiers pillaged the city at will. As the Syracusans couldn't reunite their forces and they were about losing everything, they sent an embassy, which rushed toward Lentini. They jumped from their horses, kneeling before Dion with tears on their eyes, and, in a consequent assembly, they related the events. Then, weeping emotionally, Dion could utter: "Peloponnesians and Sicilians! I have convoked you so you may decide your own actions. For my part, I am decided already, to perish for my nation at Syracuse, whether victoriously or not. Remember that I have been with you in many battles. However, neither I have deserted you at your worst moments nor I will disappoint my nation, at its worst adversity." The entire assembly burst, with euphoric shouts, and Dion announced that (after a supper) all soldiers should muster, to march toward Syracuse, on that same night.
However, learning about Dion's imminent arrival, the despot decided, burying the entire Syracuse together with his own spurned despotic dreams, so he ordered to his men that the urban center should be ignited. During that night, the entire Syracuse burned while its citizens were slain, throughout the streets. On the next day, the now popularly demanded Dion mustered, at the Syracusan Hecatompedon, dispatching his light troops (to encourage the Syracusans, right away) and commending all the available troops (which could be gathered), to the respective military leaders. Subsequently, Dion headed the troops splendidly, across the streets, cheered by the local people. However, whereas the enemy had hidden, behind the destroyed palisade of the acropolis, the liberating soldiers were unable, to reach it, through the intense fire and its dense smoke. They were the Syracusans, who encouraged spontaneously, to charge onto the enemy, which ended retreating back into the fortification. Dion captured 2,000 enemies (who were ransomed later). However, they couldn't celebrate much for (then) they had, to deal with the blazing Syracuse and its reconstruction. Nonetheless, with both the local people and his own soldiers, Dion rebuilt the palisade of the acropolis, during a single night.
Regaining the Syracusan power
During the next days, most popular leaders of Syracuse fled, being ashamed after mistreating Dion even during their worst hour. Amongst the few who remained around, Heracleides was. The foreign mercenaries of Dion suggested that he should be executed, to extirpate the so complicated populism. However, Dion amnestied his political adversaries, in accordance with his philosophical principles of political tolerance.
Confronting the other popular leader
Then, before a public assembly, the euphoric Heracleides proposed that Dion should be appointed general of full powers, again. The Syracusan aristocracy backed this but the Syracusan sectors (who had been supporting Heracleides, historically) refused accepting that their leader might lose his traditional Admiralty. Dion acceded to this however (soon) the Syracusans began insisting once again, about redistributing both the land and the houses. Dion spurned this utterly therefore, with his fleet, Heracleides moved to Messene where he gathered his political forces, aggressively. Furthermore, Heracleides sought an accord with Dionysius, through the Spartan Pharax, and, by this reason, at Syracuse, both the aristocracy and the army divided their political support between both political leaders. Syracuse plunged thus, into a disorganized crisis, lacking its regular provisions. Pharax camped at Agrigentum and Dion marched thither. After a minor battle, Dion learned that Heracleides would take advantage, landing at Syracuse during his absence, to seize it. Then, with his best men, Dion rushed through 140 km, back to Syracuse, during just one night, and (with such well timed arrival) he prevented the debarkation of the rebels.
Hopelessly, Heracleides sailed around, until encountering the Spartan Gaesylus (who expected reclaiming the Syracusan government, on behalf of this nation). To this, Dion responded: "Here, in Syracuse, we have enough generals already. Besides, (even) I have been made Spartan so I could serve this nation likewise, just like you." Gaesylus was so met with such response that, declining his original aspiration, he promised chastising Heracleides if he might attack Dion again. After this event, (furthermore) Dion disbanded the expensive Syracusan navy (which had been so conflictive, in the hands of the populists).
Expelling the tyranny
By Dion, the acropolis was subsequently cloistered by a new wall and its beleaguered occupants ended surrendering both the site and its contents. On the day on which Apollocrates abandoned the site (with five vessels, toward the Italian peninsula), the entire Syracuse gathered around, to witness such historical day (after 50 years of oppression). Then, Dion reunited emotionally, with Aristomache, Arete, and the young Hipparinus, bidding them so (again) all lived together, at his residence.
Also, Dion spent the majority of his own possessions for presents, which were given to his friends, to his foreign mercenaries, and to anyone who had contributed to his cause. Indeed, Dion was, amongst the most famed Mediterranean leaders, and he corresponded constantly, with the Athenian Academy, showing much interest for the opinion of its philosophers.
His new regime
However, Dion's government was characterized by some totalitarian impulses. To begin with, he could distance never from his so strong despotic family ties, being permanently suspected by the people. Besides, the people resented always, against his foreign mercenaries, who arrogated most executive functions of Syracuse. Furthermore, Dion disliked the democracy (because it was too haphazard) so he attempted implementing a regime, in which an aristocratic senate might take most decisions (with little popular participation). For this, Dion attempted copying the government models, which existed at Sparta, Crete, and Corinth, bringing some Corinthian politicians (who were integrated, right into Dion's court).
Then, Heracleides refused joining the aristocratic senate (after an invitation of Dion) and, again, the populist leader began conspiring. He protested because Dion hadn't leveled the acropolis, after he had barred the profanation of Dionysius' tomb, and because he had brought the foreign politicians. Then, Dion countenanced that his most virulent partisans (who desired this, long time ago) slew Heracleides (at his own home). Although (solemnly) Dion led the magnificent funeral of the popular leader, with his foreign mercenaries; the assassination was quite resented popularly, as a serious blot of Dion's regime.
The Syracusan assembly 'supplicated Dion as a god with prayers' when he returned to Syracuse (Plutarch, Life of Dion 29.2). However, Diodorus (16.20.6) described these honors as heroic .
Callippus built a conspiracy, gathering the already many sectors which were resenting Dion, to oust him. Indeed, the Athenian began gaining the trust of Dion, informing him with the many rumors, which circulated inside the army against his regime (although many weren't truthful, actually). Thus, an actual plot was built although Dion kept believing in his honesty (discrediting those, who denounced the actual plan of Callippus, to him).
Then, Dion's son committed suicide and Callippus spread the rumor that Dion would recall Apollocrates (who was his closest relative) so he would be his successor. At this point, the conspiracy was widely known and Dion said: "If (beside my usual foes) I may fear my own friends; opening my chest to the treacherous dagger, I would prefer being slain in a thousand occasions, before enduring such menace longer." Then, Callippus convoked both Aristomache and Arete (who were investigating) at the temple of Persephone, forswearing against the rumors by the great oath of the goddess. However, (ironically) he scheduled the assassination of Dion, precisely for this goddess' celebratory day.
On that date, Dion was celebrating at home with his friends. The assassins were Zacynthians, who wore light garments and who were unarmed. They walked into the house while (behind) many other accomplices began shutting all doors and windows (restraining these). The Peloponnesians jumped onto Dion, choking his throat and mashing his body, however they were unable still, to assassinate him. While the many witnesses didn't dare intervening (fearing for their own lives), to the outside, the killers screamed, beseeching for some weapon. Minutes later, a short Spartan sword (which was richly ornamented) was dropped into, by the Syracusan Lyco. Dion was trembling fearfully when (with it) his own foreign mercenaries stabbed him, to death.
Mary Renault's historical novel The Mask of Apollo tells the story of Dion and his relationship to Plato and his Syracusan predecessors through the eyes of an itinerant tragic actor.