At the height of the Cold War, William S. Lind tells us, a U.S. Army Corps commander in Europe asked for information on his Soviet opposite, the commander of the corps facing him across the inter-German border:
All the U.S. intelligence agencies, working with classified material, came up with very little. He then took his question to Chris Donnelly, who had a small Soviet military research institute at Sandhurst. That institute worked solely from open source, i.e. unclassified material. It sent the American general a stack of reports six inches high, with articles by his Soviet counterpart, articles about him, descriptions of exercises he had played in, etc.