In Greenmantle, by John Buchan, an American man, John S. Blenkiron, was on a secret mission in Turkey during the First World War. He blended in with some of his enemies there and was convincing them to recruit his friend, Richard, whom he was talking to now:-
I argued that unless I had a very clear part with a big bluff in it I wouldn’t get the confidences which I needed. We’ve got to be at the heart of the show, taking a real hand and not just looking on. So I settled I would be a big engineer—there was a time when there weren’t many bigger in the United States than John S. Blenkiron. I talked large about what might be done in Mesopotamia in the way of washing the British down the river. Well, that talk caught on. They knew of my reputation as an hydraulic expert, and they were tickled to death to rope me in. I told them I wanted a helper, and I told them about my friend Richard Hanau, as good a German as ever supped sauerkraut, who was coming through Russia and Rumania as a benevolent neutral; but when he got to Constantinople would drop his neutrality and double his benevolence. They got reports on you by wire from the States—I arranged that before I left London. So you’re going to be welcomed and taken to their bosoms just like John S. was. We’ve both got jobs we can hold down, and now you’re in these pretty clothes you’re the dead ringer of the brightest kind of American engineer ... But we can’t go back on our tracks.
How can he be a good German and American at the same time? Does it mean he was just of a German origin?