[BBell]

I looked up Ernst Witt.

From 1937 until 1979, he taught at the University of Hamburg. He died in Hamburg in 1991, shortly after his 80th birthday.

You can take that with a grain of wiki.

[MUDDOG]

The German wikipedia entry for Witt has a long discussion of his SA membership, but not the anecdote about the encounter with the Russian mathematician.

Ernst Witt

There are English bios out there, which is where I read the Russian anecdote. I believe it.

[Nifster]

Here is an accurate and in depth biography

http://www-history.mcs.st-and.ac.uk/Biographies/Witt.html