Dear David,

> I've read once a text of a dialogue between Buddha and a General (or a
> militar person), but I don't recall where I found it. I would
> appreciate if someone could point me to which sutta is this.

Probably you mean Siha sutta (AN 8.12)

Sihasuttam - The general Siha.

At one time The Blessed One was living in the gabled hall in the Great
Forest in Vesali. At that time many well known Licchavis assembled and
seated in the assembly hall were talking in praise of The Blessed One,
the Teaching and the Community of bhikkhus.

The general Siha was also seated in that gathering and it occurred to
Siha ßWithout doubts The Blessed One should be worthy and rightfully
enlightened that these well known Licchavis assembled and seated talk
the praise of The Blessed One, the Teaching and the Community in various
ways." Then the general Siha approached Nigantha Nataputta and said to
him:"Venerable sir, I desire to approach the recluse Gotama."

...

http://www.metta.lk/tipitaka/2Sutta-Pitaka/4Anguttara-Nikaya/Anguttara5/8-atthakanipata/002-mahavaggo-e.htm

> I found some portions of it in the internet but without any reference
> to where it belongs to. Actually, I am wandering if this is a autentic
> buddhist text.

There is a widespread forged version of the text, which found its way in
the book by Helena Roerich "Foundations of Buddhism" and the book by
Venerable K. Sri Dhammananda Maha Thera "What Buddhists Believe"

http://www.budsas.org/ebud/whatbudbeliev/290.htm

Someone took the beginning and the end of the sutta, and inserted his
own text in the middle.

Best wishes,
Dmytro