An army travels on its stomach

An army travels on its stomach
What is the most common meaning of this phrase?

As a non-native English speaker influenced very much by my national idioms I sense three meaning:

1. One must work hardly to get any result.
2. Any progress may be slow.
3. A good soldier is a soldier well fed.

I will be grateful for any comments and explanations.
Thank you.
Valeriy

#3 is correct. It's a quote from Napoleon Bonaparte.

A comment on your proposed answer no. 1. "One must work hardly..." While there is an adverb "hardly," the adverb to go with the adjective "hard"
is the adverb "hard". "Hardly" has come to mean something else--barely, almost not, or even "not by a long shot." There's a big difference between "He's hardly working" and "He's working hard"--or "one must work hard."
SS

Napoleon of course originally said this in French - "une armée marche à son estomac". It is normally translated into English as "An army *marches* on its stomach". He meant that an army's success depends on logistics; however brave and dedicated the soldiers are, if they have no food they cannot march or fight.(VSD)