Which war proved pivotal for the development of Marine Corps amphibious doctrine?

The development of Marine Corps amphibious doctrine was significantly influenced by World War II, which featured numerous amphibious operations that demonstrated the effectiveness and necessity of such tactics. During this war, the U.S. Marine Corps conducted several high-profile amphibious assaults, including the landings at Guadalcanal, Tarawa, and Iwo Jima. These operations showcased the challenges and complexities involved in moving troops from sea to land and emphasized the importance of combining naval and ground elements to achieve military objectives.

The experiences garnered from these operations led to a more refined understanding of logistics, coordination, and assault techniques that defined amphibious warfare. This pivotal period also prompted the development of specialized training and equipment, which further enhanced the Marine Corps' capability to conduct successful amphibious operations in future conflicts.

The other wars listed did contribute to the Marine Corps' operational history, but World War II was the defining period that established and evolved the amphibious doctrine that remains foundational to Marine Corps operations today.