The missing key event that aligns with the military campaigns during the New Kingdom period in ancient Egypt would be B. Hittites and Mitannians in Palestine.
During the New Kingdom (1550-1065 BCE), Egypt engaged in significant military campaigns in regions where the Hittites and Mitannians were present, particularly in Palestine. The Hittites were a major power that Egypt interacted with during this era. The other options (Neo-Assyrians, Persians, and Thebes) either refer to different periods or do not represent a specific military campaign relevant to the New Kingdom context.