Ptolemy I was the real founder of the Ptolemaic Dynasty in Egypt. He started to rule as a satrap. After the end of the Babylon conference, Predicass (who became the regent of the throne) gave Ptolemy little money and few soldiers ordering him to move to Egypt to run its affairs. Ptolemy I didn't like Predicass because he gave him little money and soldiers. However, he went to Egypt and entered for the first time to Egypt through Memphis. Once he arrived in Egypt, he decided to get rid of Clemenes.
Clemenes, a great banker from Naucratis, was a close friend to Predoicass and he was appointed as the Chief Administrator of Egypt by Alexander. It is significant to mention that Clemenes had a greedy nature: he exploited the Egyptians, bought the wheal from the Egyptian peasants with the lowest price then he stored the wheat until a starvation happened, then he sold the wheat during the starvation with the highest price and the difference between the two prices went to his own pocket. For all that is mentioned, combined with the fact that he was the sole buyer for the wheat, the Egyptians complained to Ptolemy I. On his part, Ptolemy I took these complaints as a chance and arrested Clemenes and put him in trial. After found guilty, Clemenes was executed.
Moreover, Ptolemy I confiscated Clemenes' wealth for the benefit of the Egyptian treasury. This was the first act that upset Predicass from Ptolemy I.
The second instance that upset him from Ptolemy I took place when a civil war broke out in Libya between the Greeks who settled on the Libyan Coast. They sent for Ptolemy I to help them to restore order and law there, then he annexed Libya to Egypt without taking the permission of Predicass.
The third instance occurred when Predicass sent a letter to Ptolemy I asking him to send a list of the revenue of Egypt, however, Ptolemy I refused.
Based on these reasons, Predicass felt that Ptolemy I was defying him and planning for independence. Therefore, Predicass decided to put an end for the rule of Ptolemy I by preparing an army. He began to head to Egypt until he reached the Nile at a point near Memphis in 321 BC, then he decided to cross the Nile, but, Ptolemy I was waiting with his army at Memphis. The crossing of the Nile was difficult at that time because it was during the inundation season, so Predicass sent a group of soldiers to cross the Nile but they were all drowned then he sent another group but also they all died . When Predicass went to his tent to have some rest before the third attempt, his chief officers went after him then killed him and asked Ptolemy I to be the new regent of the Macedonian throne . Ptolemy I refused their offer and he provided the army with support and sent the army back to Macedonia, thus Ptolemy I was saved without any fighting.
In 305 BC, when the whole royal Macedonian family was killed, Ptolemy I was declared as the new king of Egypt and the founder of the Ptolemaic Dynasty.
In 305 BC, Ptolemy I declared his independence from the Macedonia and Greek Empire. In 285 BC, Ptolemy I retired and took his eldest son, Ptolemy II, to be his co-regent. Two years later, Ptolemy I died in 283 BC and was followed by his son Ptolemy II.