Which rank is designated as O-6 in the Marine Corps?

In the Marine Corps, the rank designated as O-6 is Colonel. This rank reflects a position of significant responsibility, as Colonels typically command large units, such as regiments or similar-sized formations, and are involved in higher-level strategic planning. The rank of Colonel is an important milestone in a Marine's career, as it signifies the transition from operational leadership to a role that also includes administrative and logistical responsibilities.

Lieutenant Colonel, which is the O-5 rank, is one level below Colonel and also holds important command roles but with fewer responsibilities compared to a Colonel. Brigadier General is an O-7 rank, representing the first level of general officer, indicating a rank above Colonel. Major, an O-4 rank, is yet another level down and focuses primarily on company or battalion-level operations. Understanding these hierarchical structures is crucial for grasping how military operations are organized and managed.