Geneva Conventions didn’t exist until AFTER WW2. fair amount of stuff the Allies did is considered War Crimes as well, I.E. the Dambusters.

Mark’s unusually high degree of civility towards “the cousins” inclines me to think he has no official relation with HM’s government services at all… MI5 et all were barely on speaking terms with the OSS etc during the war… and as others have pointed out, we basically OWNED Asia up until the end of WW2

To persist, devilish.

Taking blood from POWs? I think that might be not in accordance with the Geneva Convention. Nice thought for future novels – vampires in ww2.

Well, but being around might be a bigger bonus.

Being the only person she doesn’t accidentally mind scan might be a bonus.

You can take reasonnable amount of blood from multiple people rather than deadly amounts from one. I’m assuming vampires, like vampire bats, are capable of feeding without waking it’s prey and can help the wound heal. A few civilian feel a bit lightheaded after waking up and need a good breakfast, when he’s on the frontlines he could even feed on the ennemies.
Worst case scenario, if it turns out that being a vampire blows because you have to drain a person completely every night well… it IS war, they probably have prisonners. That seem unlikely though.

It’s always dirty biz. LOL

And how you supply him with “juice”?

I would not. Secret agents have a too unstable private life.