In chapter 27 of the Saga of the Völsungs, Brynhild brags of having been in battles with a king of Greeks:
She answered in heavy mood from her seat, whereas she sat like unto swan on billow, having a sword in her hand and a helm on her head, and being clad in a byrny, "O Gunnar," she says, "speak not to me of such things unless thou be the first and best of all men; for then shall thou slay those my wooers, if thou hast heart thereto; I have been in battles with the king of the Greeks, and weapons were stained with red blood, and for such things still I yearn."
"Chapter 20", The Story of the Volsungs, translated by William Morris and Eirikr Magnusson
Is this Brynhild's way of saying she has battled legendary opponents in far away lands, or could it be a more specific reference? Given that Brynhild's brother King Atli is identified with Attila the Hun, could this perhaps be a reference to Attila's campaigns against the Eastern Roman Empire?