Re: US military services
"I'm not American: in countries where I am a national the Coast Guard is a branch of the Navy, so it never occurred to me that it wasn't part of the USN."
In the US, the Coast Guard is nominally a police force and not military. The difference is how they are allowed to be used on US soil. The definition is a bit gray by not being entirely police or entirely military, but biaed more towards police. Training can be different too. Those in the military are taught to kill, and the police are expected to use deadly force as a last resort.