How did a Greek family rule Egypt as pharaohs for 300 years?

They ruled by dressing up as Egyptians while staying Greek underneath. When Alexander the Great died in 323 BC, his general Ptolemy kept Egypt and, in 305 BC, made himself its king. His family, the Ptolemies, ruled for nearly three centuries, until Cleopatra died in 30 BC: the longest and the last dynasty of ancient Egypt.

To be accepted, they borrowed the old symbols of power. They took the title of pharaoh and had themselves carved on temple walls in Egyptian dress. They issued decrees in three scripts, hieroglyphs, Demotic and Greek, which is exactly what the Rosetta Stone is. Ptolemy I even created a brand-new god, Serapis, who mixed the Egyptian Osiris and Apis with the Greek Zeus and Hades, to win over Greeks and Egyptians at once. His son went further and married his own sister, following an Egyptian custom that pleased his subjects.

Behind the costume, the court stayed Greek. A Greek ruling class held power and rarely mixed with Egyptian society. It did not always work: from 205 to 186 BC, a priest named Horwennefer proclaimed himself pharaoh and his son nearly drove the Ptolemies out. The most telling detail comes at the very end: Cleopatra is the only Ptolemaic ruler known to have learned to speak Egyptian.