While conducting my research in the Vienna War Archives, I discovered a document or a manuscript, written in Croatian, in the collection of records about Captain Mocnay and his return from Russia. It turned out that this was a meticulous transcription of the work entitled Srpski dobrovolj. korpus (Serbian volunteer corps), published in the Jugoslavia (Yugoslavia) newspaper, coming out in Russia in 1916 and 1917. The following contribution provides a short presentation of the biographical information about the aforementioned Captain Mocnay; and the published transcript of the document discovered represents, in a way, an encouragement that – on the basis of such documents – some light should also be shed on the outlook of the Habsburg authorities on the very formation of volunteer units in Russia.