The Issue Wonk has a diary up on Daily Kos discussing the history of the estate tax. As I wrote in my comment on the diary, I find it fascinating that the estate tax has been levied at various times in American history to raise funds for military expenditures, and repealed shortly thereafter--except for the latest round to fund WWI, which continues to this day.
Republicans have reversed this. They are now eliminating the estate tax during a time of war. Unconscionable.