That a political ruler held his power by favor of a god or gods—or that he was a living incarnation of a god—became firmly established in Egypt

They use of hieroglyphics—a form of writing that used images to express sounds and meanings—likely began in this period.

The Nile River flooded annually; this flooding was so regular that the ancient Egyptians set their three seasons—Inundation, or flooding, Growth, and Harvest—around it.
This annual flooding was vital to agriculture because it deposited a new layer of nutrient-rich soil each year. In years when the Nile did not flood, the nutrient level in the soil was seriously depleted, and the chance of food shortages increased greatly.

During the Old Kingdom period, Egypt was largely unified as a single state; it gained in complexity and expanded militarily. Old Kingdom rulers built the first pyramids, which were both tombs and monuments for the kings who had them built.

Great Pyramid,Sphinx in Giza...

Egyptians also began to build ships, constructed of wooden planks tied together with rope and stuffed with reeds, to trade goods such as ebony, incense, gold, copper, and Lebanese cedar—which was particularly important for construction projects—along maritime routes.

The Middle Kingdom saw Egypt unified again as kings found ways to take back power from regional governors. From the Middle Kingdom era forward, Egyptian kings often kept well-trained standing armies. The ability of the Egyptian state to create and maintain a standing military force and to build fortifications showed that it had regained control of substantial resources.

Around 1550 BCE, the New Kingdom period of Egyptian history began with the expulsion of the Hyksos from Egypt and the restoration of centralized political control. This period was Egypt's most prosperous time and marked the peak of its power.

Also in this period, Hatshepsut, Egypt’s most famous female ruler, established trade networks that helped build the wealth of Egypt and commissioned hundreds of construction projects and pieces of statuary, as well as an impressive mortuary temple at Deir el-Bahri. She also ordered repairs to temples that had been neglected or damaged during the period of Hyksos rule.

New Kingdom Egypt reached the height of its power under the pharaohs Seti I and Ramesses II, who fought to expand Egyptian power against the Libyans to the west and the Hittites to the north. The city of Kadesh on the border between the two empires was a source of conflict between the Egyptians and the Hittites, and they fought several battles over it, ultimately agreeing to the world’s first known peace treaty.