Who was the Commandant credited with guiding the Marine Corps?

General John A. Lejeune is often credited with guiding the Marine Corps during a pivotal time in its history. He served as the 13th Commandant of the Marine Corps from 1920 to 1929 and is recognized for establishing the modern structure and doctrine of the Corps. His leadership emphasized the importance of amphibious operations, which became a cornerstone of Marine Corps strategy and tactics, especially during World War II.

Lejeune's focus on the importance of education within the ranks helped foster a professional development philosophy that remains a foundational element of Marine Corps culture today. Furthermore, he was instrumental in strengthening the ceremonial aspects of the Marine Corps, contributing to the Corps' identity and public image.

In contrast, while other figures such as General James Mattis have made significant contributions, they operated in more modern contexts and did not play a role similar to Lejeune's in shaping the Marine Corps' core principles. Captain Samuel Nichols was the first officer commissioned in the Marine Corps, and Admiral Chester Nimitz, though an important figure in naval history, was not directly involved with the leadership or guidance of the Marine Corps as Commandant.