Which rank corresponds to an O-3 in the Army?

In the Army, the O-3 rank is identified as Captain. The rank structure uses a system where "O" denotes an officer, and the number following it indicates the grade within the officer ranks. In this case, an O-3 signifies the third level of officer ranking, which is indeed Captain.

A Captain typically commands a company-sized unit, which is comprised of around 100 to 200 soldiers, and their responsibilities often include leadership, planning, and the execution of missions. This rank is also crucial because it serves as a bridge between junior officers and more senior leadership, providing vital experience in team management and operational execution.

First Lieutenants, who hold the O-2 rank, are generally seen as junior leaders and may assist Captains in various duties. The ranks of Major (O-4) and Lieutenant Colonel (O-5) come at higher levels of seniority and responsibility, focusing more on broader command structures and strategic oversight.