The Seleucids and the Parthians vie for control of the independent Bactrian state.

In 170, Antiochus dispatches a force under Eucratides to conquer Bactria.

Parthia’s Mithridates I attacks Bactria’s frontiers while its ruler, Demetrius, is occupied with repelling the Seleucid invasion.

The causes of the Sixth Syrian War are obscure.

Eulaeus and Lenaeus, the two regents of the young king of Egypt Ptolemy VI Philometor, in 170 declare war on Antiochus.

In the same year, Ptolemy's younger siblings Ptolemy VIII Physcon and Cleopatra II are declared co-rulers in order to bolster the unity of Egypt.

Antiochus, taking advantage of Rome’s prosecution of the third Macedonian War, meanwhile forestalls the Egyptian expedition to Palestine by invading Egypt.

The Romans have problems with discipline in their army, and Roman commanders, who cannot find a way to successfully invade Macedonia, devote more effort to plunder than to the defeat of Perseus.

In a notorious incident, the praetor Lucius Hortensius anchors his fleet on the Thracian coast at Abdera, a city allied with Rome, and demands supplies; when the Abderitans ask to consult the Senate, Hortensius sacks the town, executes the leading citizens, and enslaves the rest.

When complaints reach the Senate, weak attempts are made to force the Roman commanders to make restitution.

…the Chaones and …

…Thesproti siding with Rome.

The Egyptians realize their folly in starting the war, Eulaeus and Lenaeus are overthrown and replaced by two new regents, Comanus and Cineas, and envoys are sent to negotiate a peace treaty with Antiochus.

Antiochus takes Ptolemy VI (who is his nephew) under his guardianship, giving him effective control of Egypt.

Antiochus thus gives Rome no excuse for intervention.

This arrangement is, however, unacceptable to the people of Alexandria, who respond by proclaiming Ptolemy Physcon as sole king.

Antiochus besieges Alexandria but he is unable to cut communications to the city.

As he needs also to deal with the civil war in Judaea so, he withdraws his army at the end of 169.

In his absence, Ptolemy VI and his brother are reconciled.

Syrian military operations do not begin until 169 BCE, when Antiochus defeats the Egyptians between the important strategic frontier city of Pelusium and Mount Kasion, seizing Pelusium and occupying Egypt with the exception of Alexandria, the capital.

Antiochus' ouster of Jason has meanwhile occasioned a civil war in the Jewish temple-state, with the wealthy aristocrats supporting Menelaus and the masses, Jason.

While Antiochus is campaigning in Egypt, a rumor spreads that he had been killed.

The deposed High Priest gathers a force of one thousand soldiers and makes a surprise attack on Jerusalem.

Jason conquers Jerusalem, with the exception of the citadel, and murders many adherents of his rival, Menelaus, who is forced to flee the city.

Antiochus safeguards his access to Egypt with a strong garrison in Pelusium.

There is a stalemate near Phalanna involving Perseus and Crassus.

Consul Quintus Marcius Philippus in 169 BCE crosses the Olympus Range and enters Macedon.

His army runs out of provisions, however, and retires on a narrow strip of coast near Tempe.