... bound to the north and west by the Rivers/rivers Danube, Sava and Drina.

[Leyland]

Should 'rivers' be capitalised here?

In 1914, Serbia was bound to the north and west by the Rivers Danube, Sava and Drina.

Or:

In 1914, Serbia was bound to the north and west by the rivers Danube, Sava and Drina.

 

[emsr2d2]

Should 'rivers' be capitalised here?

1. In 1914, Serbia was bound to the north and west by the Rivers Danube, Sava and Drina.
Or:
2. In 1914, Serbia was bound to the north and west by the rivers Danube, Sava and Drina.

Please note that I have improved your thread title and moved your actual question to the main body of the post. Titles should be unique and relevant, and should include some/all of the words/phrases/sentences you are asking us to look at. Also, when you give us more than one sentence to look at, please number them.

There is no need to capitalise "river(s)" before the name of a river. You can read more HERE.