In which two conflicts did the Marines serve during World War II?

The two conflicts in which the Marines served during World War II as highlighted in the chosen option are significant battles that played crucial roles in the Pacific Theater of the war. Saipan, part of the Mariana Islands, was a pivotal battle that led to the capture of a strategic location allowing for the bombing of Japan. The battle of Guadalcanal is notable as it marked the first major offensive by Allied forces against the Empire of Japan, setting the stage for the subsequent island-hopping campaign.

Both Saipan and Guadalcanal demonstrated the commitment of the United States Marine Corps to securing vital territories and learning from previous engagements to improve tactics and strategies against Japanese forces. As Marine forces faced both intense combat and logistical challenges in these battles, their success helped to shift the momentum of the war in favor of the Allies.

The other options include engagements that, while significant in their own right, do not align as precisely with the question regarding the two conflicts specifically attributed to the Marine Corps during World War II.