Egypt became a powerful and aggressive land at the time of the New Kingdom. It was conquering Nubia and was at war with the Near East at the same time. The Pharaohs began to lead campaigns since the time of Thutmose III. to strengthened the power over the east. The main enemy of Egypt was the Kingdom of Mitanni then, which was located on the north of Syria. It was important for Egypt to strengthen its dominance over an area extending from Palestina up to Caucasus from both political and economical point of view. It would enable Egypt to seize control over Phoenician coast and main caravan ways leading to Mesopotamia.
Kingdom of Mitanni was extended to northern Mesopotamia and north-eastern Syria, where Khabur River valley was its centre. It was allegedly founded by Hurrian and Aryan warriors, who came there from Caspian Sea area. These nations were of Indo-European origin and they subdued the native inhabitants, who were focused on agriculture. Mitanni originated in the area conquered in Hammurabi's Babylonia. It was situated to the south from the Caucasus on the up-river of Tigris and it gradually extended to the area between Euphrates and Tigris rivers.
The Kingdom of Mitanni gained the biggest growth in the 15th century BC. Mitanni wanted to retain its dominancy in this area, so it tended to involved Egypt into local wars that shouldn't spread out of Syria and threaten the Kingdom borders. So Mitanni hadn't no scruples and provoked conflicts between Asian principalities and Egypt (and we have to admit that it did it very skilfully) and it changed the allies very often.
Mitanni vs. Thutmose III.
The Egyptian dominancy was threatened in this area under Amenhotep I. rule around 1,510 BC. When Thutmose III. came to the Egyptian throne, he had to suppress the rebellion of Asian principalities, which formed a coalition influenced by Mitanni. So Thutmose started the first of 17 campaigns against Mitanni. He conquered Palestina, gained Gaza and Tyre and he also seized the cities to the south from Aleppo later.
Thutmose built fortresses along the Mediterranean coast during four following campaigns. He made a journey every year to control the conquered areas, took out tributes and confiscated grain crop. He got into Syria through the sea during his sixth campaign, got up to Kadesh and plundered the whole area. Then he subjugated Phoenician harbours next year during the seventh campaign.
Thutmose wanted to continue with conquests, so he had to fight with people of Mitanni in an open battle. He needed to cross the Euphrates river for it, therefore he let build a vast flotilla of boats. Then he crossed the Orontes river and Euphrates river as well and got to the gates of Aleppo - a Mitanni bastion. After conquering Aleppo were Babylon, Assur and the whole Hittite Kingdom at the mercy of the Pharaoh. Thutmose tried vainly to weaken Mitanni soldieries in the northern area of Naharin during next nine campaigns. His last campaign ended the conflicts between people of Mitanni and the Egyptians for almost ten years.
Mitanni vs Amenhotep II
Thutmose was replaced by his son Amenhotep II. on the throne, who had an exceptional power. He made three campaigns into Syria - the aim of the first campaign was to suppress a rebellion of Asians. He got up to the borders of Mitanni, whose princes begged the Pharaoh to let them "breath at least". The two other campaigns were aimed directly against Mitanni, but it finished by a failure and loss of the area between the Orontes and Euphrates river.
Former enemies, now allies
After Amenhotep II. his son Thutmose IV. came to the throne and the relationships between Egypt and Mitanni gathered a new course. People of Mitanni tried to get close with a former enemy, because they were threatened by a new originated Hittite Kingdom, which especially warred in Anatolia up to then. And there also was another enemy - the Assyrians on the east.
People of Mitanni conclude a contract with Egypt. They left Palestina and part of the Mediterranean coast to Egypt and got the northern part of Syria in exchange for it. Thutmose IV proposed one of Mitanni king's Artatama I daughters to seal the alliance.
Also Amenhotep III. continued with the politics of his father. Boards with diplomatic correspondence between Amenhotep III, Amenhotep IV. - Akhenaten and the rulers of Babylonia, Assyria, the Hittite Kingdom and the Kingdom of Mitanni were founded. Amenhotep III. clinched the alliance between Mitanni and Egypt with a marriage with Tadukhipa - a daughter of Tushratta.
But the situation was critical for Mitanni - even this alliance didn't save it before the Hittite Kingdom. The Hittites were subordinated to Mitanni before, but led by the king Suppiluliuma I they conquered the whole area of Mitanni during two campaigns and they imposed its king a vassal treaty. Mitanni ceased to exist definitively around 1,355 BC, when the capital Washukanni was conquered by the Hittites.