In late 142 or early 141 BC, Antiochus VI Dionysus died, supposedly during a medical operation; most ancient sources accuse Diodotus of having had the young king murdered.
Diodotus convinced the army to elect him king.

Royal titles and representation
As king, Diodotus used the name Tryphon Autocrator. '
Tryphon' referred to the Hellenistic royal virtue of tryphe (luxury).
Tryphe was sometimes a negative attribute, implying softness, but could also be a positive virtue, advertising the ruler's wealth and ability to reward his subjects.
The epithet Autokrator is unique; it is not attested for any other Greek ruler from this period.
Edwyn Bevan argued that this epithet was intended to recall the Macedonian kings Philip II and Alexander the Great, who had held the title of Strategos Autokrator as elected leaders of the Greek forces against Persia.
In Bevan's view this reference indicated Tryphon's election as king by the 'free Greco-Macedonian states of Syria'.
Boris Chrubasik argues that Tryphon took the epithet in imitation of the Parthian rulers and to emphasise his independence from his predecessors (the term Autokrator literally means 'ruling (by) himself').
The marital overtones of it perhaps served to counter the implications of softness that sometimes were associated with tryphe.

There is no sign that Tryphon considered himself to be part of the Seleucid dynasty.
On the contrary, he emphasised the break with his Seleucid predecessors through his unusual title, as well as the iconography of his coinage.
His coins depicts him in a mature guise, with a rather fat face and long flowing hair - emphasising the luxuriousness implied by the name Trypon.
The reverse side of his coins depict an elaborately decorated Boeotian helmet.
This might have been meant to extend his connection to the army, and/or to further emphasise the idea of martial luxury.
The break with the Seleucids was also indicated by the abandonment of the Seleucid dating system, in which years were counted continuously from the rise to power of Seleucus I. Tryphon instituted a new system, counting from his own accession as king.

In order to secure Roman recognition of his kingship, Tryphon sent a golden statue of the goddess Nike to Rome.
The Roman Senate chose to accept this Nike as a gift from Antiochus VI and did not extend recognition to Tryphon.
There is no evidence that any of the neighbouring kings recognised Tryphon's kingship either.

War against Demetrius II and Antiochus VII
Once he was king, Tryphon expanded his control to at least Ptolemais-Akke and Dor.
Demetrius, meanwhile, had journeyed east in 139/8 to fight the Parthians, who had seized control of Mesopotamia the previous year.
He was defeated and captured by them July or August of 138 BC, leaving Tryphon as uncontested ruler of the remaining Seleucid territories.

Almost immediately, however, Demetrius' brother, Antiochus VII Sidetes took up the conflict against Tryphon.
He declared himself King Antiochus Euergetes, left his home in Rhodes, and landed in Phoenicia in the face of staunch resistance.
He married the wife of Demetrius, Cleopatra Thea, further legitimizing his position.
Numismatic evidence shows that many coastal cities remained loyal to Tryphon, but that Sidon and Tyre immediately attached themselves to Antiochus' cause.
Antiochus also successfully won over Simon Thassi by confirming and augmenting the grants made by his brother.

Antiochus defeated Tryphon in battle and took control of Antioch by the middle of 138 BC.
He moved south to the fortress-city of Dor, where he was besieged.
From there he escaped by sea to Orthosia and made his way to his home-region of Apamea, where he was besieged again died in late 138 or early 137 BC.
Some sources say he was captured and executed, others that he committed suicide.
In late 142 or early 141 BC, Antiochus VI Dionysus died, supposedly during a medical operation; most ancient sources accuse Diodotus of having had the young king murdered. Diodotus convinced the army to elect him king.
Royal titles and representation
As king, Diodotus used the name Tryphon Autocrator. 'Tryphon' referred to the Hellenistic royal virtue of tryphe (luxury). Tryphe was sometimes a negative attribute, implying softness, but could also be a positive virtue, advertising the ruler's wealth and ability to reward his subjects. The epithet Autokrator is unique; it is not attested for any other Greek ruler from this period. Edwyn Bevan argued that this epithet was intended to recall the Macedonian kings Philip II and Alexander the Great, who had held the title of Strategos Autokrator as elected leaders of the Greek forces against Persia. In Bevan's view this reference indicated Tryphon's election as king by the 'free Greco-Macedonian states of Syria'. Boris Chrubasik argues that Tryphon took the epithet in imitation of the Parthian rulers and to emphasise his independence from his predecessors (the term Autokrator literally means 'ruling (by) himself'). The marital overtones of it perhaps served to counter the implications of softness that sometimes were associated with tryphe.
There is no sign that Tryphon considered himself to be part of the Seleucid dynasty. On the contrary, he emphasised the break with his Seleucid predecessors through his unusual title, as well as the iconography of his coinage. His coins depicts him in a mature guise, with a rather fat face and long flowing hair - emphasising the luxuriousness implied by the name Trypon. The reverse side of his coins depict an elaborately decorated Boeotian helmet. This might have been meant to extend his connection to the army, and/or to further emphasise the idea of martial luxury. The break with the Seleucids was also indicated by the abandonment of the Seleucid dating system, in which years were counted continuously from the rise to power of Seleucus I. Tryphon instituted a new system, counting from his own accession as king.
In order to secure Roman recognition of his kingship, Tryphon sent a golden statue of the goddess Nike to Rome. The Roman Senate chose to accept this Nike as a gift from Antiochus VI and did not extend recognition to Tryphon. There is no evidence that any of the neighbouring kings recognised Tryphon's kingship either.
War against Demetrius II and Antiochus VII
Once he was king, Tryphon expanded his control to at least Ptolemais-Akke and Dor. Demetrius, meanwhile, had journeyed east in 139/8 to fight the Parthians, who had seized control of Mesopotamia the previous year. He was defeated and captured by them July or August of 138 BC, leaving Tryphon as uncontested ruler of the remaining Seleucid territories.
Almost immediately, however, Demetrius' brother, Antiochus VII Sidetes took up the conflict against Tryphon. He declared himself King Antiochus Euergetes, left his home in Rhodes, and landed in Phoenicia in the face of staunch resistance. He married the wife of Demetrius, Cleopatra Thea, further legitimizing his position. Numismatic evidence shows that many coastal cities remained loyal to Tryphon, but that Sidon and Tyre immediately attached themselves to Antiochus' cause. Antiochus also successfully won over Simon Thassi by confirming and augmenting the grants made by his brother.
Antiochus defeated Tryphon in battle and took control of Antioch by the middle of 138 BC. He moved south to the fortress-city of Dor, where he was besieged. From there he escaped by sea to Orthosia and made his way to his home-region of Apamea, where he was besieged again died in late 138 or early 137 BC. Some sources say he was captured and executed, others that he committed suicide.
Diodotus Tryphon