A more thorough explanation:

The United States Marine Corps is a branch of the United States Navy that is trained for combat on land, sea, and air. It is a separate service within the U.S. Navy and is under the authority of the U.S. Department of the Navy. The abbreviation for the United States Marine Corps is USMC.

Example: The United States Marine Corps played a crucial role in the Battle of Iwo Jima during World War II.

This example illustrates how the United States Marine Corps is trained for combat on land. During the Battle of Iwo Jima, the Marines fought on the island's rugged terrain and successfully captured it from the Japanese forces.