If I'm not mistaken, it's both. However generally sizes across the brand will be the same, and these boots have different feels, not different fits.
Nike fits slightly smaller. I've been testing out/wearing the Zoom DK's all day here in Whistler, and as a shoe size 8, the size 9's fit quite perfectly for me (my toes are touching the end. It's not a problem to me). Same thing with the ThirtyTwo boot - thread related: ThirtyTwo Sizing Accuracy Thread
I'd recommend buying the same size that you had in the forces.