How many years did Archibald Henderson serve in the Marine Corps?

Archibald Henderson served in the Marine Corps for 38 years, making this the correct answer. His tenure exemplified a significant period in the history of the United States Marine Corps, during which he played a vital role in its development and transformation. Appointed as the 5th Commandant of the Marine Corps, Henderson's leadership spanned several major conflicts and contributed to the professionalization and expansion of the Corps.

His long service is notable for the reform and modernization efforts he initiated, establishing policies and practices that would shape the future of the Marines. Henderson's commitment and long-standing service have made him an important figure in Marine Corps history, and his impact is still recognized today.