The United States military is made up of several branches, each with different responsibilities: 

1. Army - The Army is responsible for land operations. The Army also has a marine presence, with some soldiers known as "Army mariners". 

2. Navy - The Navy is responsible for maritime operations, including maintaining a forward-deployed force. 

3. Marine Corps - A component of the Navy, the Marine Corps specializes in amphibious and maritime littoral operations. 

4. Air Force - Responsible for air operations.

5. Space Force - The Space Force is responsible for space operations and is the smallest branch of the military. 

6. Coast Guard - The Coast Guard is responsible for law and maritime safety enforcement, including search and rescue missions. The Coast Guard also collects oceanographic data for environmental research.  

7. National Guard - The National Guard's mission is to defend the country, fight in wars, and help communities during disasters. 

(usa.gov)