..................  It is July 1864.  Union and Confederate forces stand deadlocked at the vital rail junction of Petersburg, Virginia.  To break the bloody stalemate, a group of coal miners from the 48th Pennsylvania Infantry Regiment tunnel beneath the Confederate earthworks and plant four tons of gunpowder.  Their plan works.  Hundreds of Confederate soldiers die instantly in an enormous explosion.  But while Federal commanders bicker and dawdle, the Southerners rally.  A near-certain Union victory quickly turns into a shocking bloodbath.  Ulysses S. Grant calls it "the saddest affair I have witnessed in the War."  ......................