The causes of the Sixth Syrian War are obscure.

In 170 BCE, Eulaeus and Lenaeus, the two regents of the young king of Egypt Ptolemy VI Philometor, declare war on the Seleucid ruler Antiochus IV Epiphanes.

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.

Military operations donot begin until 169 when Antiochus quickly gains the upper hand, seizing the important strategic town of Pelusium.

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.