"The Depression of the 1930s was marked by the spread of protectionist trade policies, which contributed to a collapse in world trade."
While Bernanke likes to point to the inability to print money as cause and elixir to the Great Depression, the fact is, about a dozen policy mistakes, not to mention a Fed induced credit bubble in the Roaring 20′s, created the Great Depression.
Trade Policy Disaster: Lessons from the 1930s (Amazon)