When Thutmose I came to power at the beginning of the 18th Dynasty, Egypt was still in a bit of a funk from the political instability of the Second Intermediate Period. The founder of the dynasty, Pharaoh Ahmose I, had inherited the throne as a child, as did his son and successor Amenhotep I decades later. While Ahmose and Amenhotep successfully drove the Hyksos invaders out of their country and restored Egypt's sovereignty, this succession of child kings (in addition to Amenhotep's inability to produce a male heir) called the future of the newly-unified Egypt and its royal family into question. That's where Thutmose comes in.
The man who would become Pharaoh Thutmose I was already middle-aged when he was named by Amenhotep as heir to the throne. Much about Thutmose's origins is a mystery: we know his mother was a woman named Senseneb (most likely a commoner) and that Thutmose served as one of the Pharaoh's senior military officers. It's also likely that he was related to the royal family by marriage, but this is unclear. Because of his age, Thutmose knew that he probably wouldn't have a lengthy reign, so immediately following his coronation ca. 1506 B.C.E., the general-turned-king got to work.
During the first year of his rule, Thutmose I launched a series of bloody campaigns against Egypt's southern neighbor and longtime rival, Nubia (modern-day Sudan). One of his first forays into the territory involved an attack on the Nubian capital of Kerma, which the pharaoh's armies razed to the ground. Thutmose erected various stelae throughout this newly-conquered territory, commemorating his expansion of the Egyptian Empire's borders for posterity. To ensure that the Nubian people wouldn't rise up against Egypt in the future, Thutmose also ordered the construction of a series of fortified towns and fortresses throughout Nubia, to house the occupying Egyptian forces and keep the locals in check.
One of the most memorable episodes from Thutmose I's Nubian campaign is how the pharaoh dealt with the ruler of Kerma. Accounts suggest that the Nubian leader was slain by Thutmose in battle, and that, as a potent symbol of the new pharaoh's might and military prowess, Thutmose sailed back up the Nile to Thebes with the body of the slain Nubian hanging from the bow of his ship. (Another ancient Egyptian military tradition? Soldiers severing and collecting the hands of their fallen enemies!)
Thutmose I is widely regarded as one of the most powerful and successful rulers of the 18th Dynasty. At a time when Egypt was still reeling from the oppression of the Hyksos, Thutmose helped to finish the work of his predecessors and quell insurrection in the south, cementing the legacy of his own family in the process. A bold leader, Thutmose I was clearly a great inspiration to his daughter, Hatshepsut, and grandson, Thutmose III, both of whom worked tirelessly to expand and protect the might and influence of the Thutmoside Dynasty and its empire.