The United States and Soviet Union stood on opposite sides of the Cold War.  Both tried to project strength and both possessed immense arsenals of nuclear weapons.  A fundamental problem for both superpowers was figuring out what the other side was doing.  What were they capable of?  What were they thinking?   The United States relied on its submarines to help answers those questions throughout the Cold War.  The missions these submarine crews went on were months long and involved great risks.  They were also carried out in absolute secrecy.  At least until now.  Sherry Sontag and Christopher Drew tell the story in “Blind Man’s Bluff.”