Tullius Hostilius was the third king of ancient Rome, succeeding Numa Pompilius. He reigned from around 673 to 642 BCE and is known for his military focus and expansionist policies. Hostilius is credited with the conquest of the neighboring city of Alba Longa, which helped to strengthen Rome's power in the region. Under his rule, Tullius Hostilius also emphasized the importance of military training and discipline among the Roman citizens. His reign is marked by a series of wars and conflicts, which contributed to the growth of the early Roman state and laid the groundwork for future military endeavors.