After the death of Ptolemy II, he was succeeded by his son Ptolemy III. He was 30 years old when he ascended to the throne.
As soon as he became the King of Egypt, news reached him about the death of the Seleucus King who was his brother-in-law and that the life of his sister and his nephew were in danger. so he decided to lead a campaign to save them. But before his departure from Egypt to Asia Minor, the news of the death of his sister and his nephew reached him. However, he continued his campaign to revenge their death. When he reached Syria, he succeeded in achieving a great victory over the Seleucus Kingdom in what is known as the Third Syrian War and he defeated the Seleucus King in a famous battle, but little was recorded about this battle.
Coele-Syria: this area was full of cedar wood and polemics in Egypt needed the cedar wood to build a strong navy and to bring the cedar wood from Coele-Syria Egypt the sixth wars of Syria took place.
Before his departure, he married his cousin Queen Bernice II, daughter of Magas (ruler of Libya). Bernice II began to rule Egypt while Ptolemy III was away in his campaign, but she couldn’t control the whole country due to some unrest accompanied by low inundation (flood) which resulted in a famine or a starvation in Egypt so when he returned back to Egypt, he distributed wheat and corn among the Egyptians to lessen the burden of famine on the population. These wheat and corn brought from Syria as booty. He also brought back some statues of the Egyptian deities which Cambyes took from Egypt few hundred years earlier. Then he used excessive force to put down the revolts of the Egyptians, as a result, he was hated by the Egyptian people.