The military force of a country is often divided in branches such as an army, a navy, and an air force. There are many other branches out there, but the point is that I am looking for a division of military power at such a high level. Are there passages from classical(ish) Latin literature that illustrate the structures of the Roman military, especially a division to branches?
One might imagine that the Roman military had an army and a navy. How were those branches called and how were they related? Did the Romans make a clear division in a way similar to what we do today? For example, I don't know whether naval forces were always subordinate to a land unit or an independent entity. I am looking for a passage that would illustrate such structures clearly enough. I am not looking for vocabulary in isolation, but passages that show relations between them.
The answer may depend on the specific era, but any insight is welcome. If there are several, then something with a distinction as clear as possible between army and navy would be great. Perhaps there was a time when one consul had the army and the other one had the navy, making for a clear equal-level division?
I am not looking for a description of all of the Roman military, but for vocabulary (used in context) having to do with branch division.