The modern Egyptian line is that pharaonic Egypt was a cohesive whole, and never knew conquest, but that’s been known to be not true since cuneiform writing was cracked. There’s evidence from the Akkadian records (they were the early dynasty of the Assyrian Empire) that Egypt paid them tribute.
Besides the Intermediate Periods after the Old Kingdom and Middle Kingdom (and per the conventional timelines, the 3rd IP after the New Kingdom and the Ptolemaic or Late Kingdom) there were dynastic collapses, and separate independent states with competing pharaohs in different parts of the river basin. That was probably inevitable since the culture(s) was distributed the length of the Nile but only a few miles wide for most of that length.
That said, they developed three different systems of writing (depending on the era and the change of ethnic and cultural composition) and adopted the use of cuneiform for international diplomacy, having developed hieroglyphic writing no later than the 2nd dynasty, and examples of precursors of the characters go back to 3300 BC, it sez here. They continued to develop hieroglyphics until they’d invented thousands of characters, a good many of which remain unreadable, as they exist in single or just a handful of examples from a brief range of years.
Yep.
Professor Brier on my “Ancient Egypt” recordings observes that the Egyptians never kept records of a military defeat: they just had “victories” closer and closer to their capital!