query: who fought in the battle of vicksburg?
answers: [ ' C o n f e d e r a t e S t a t e s o f A m e r i c a ' , ' U n i o n ' , ' J o h n C . P e m b e r t o n ' , ' U n i t e d S t a t e s o f A m e r i c a ' , ' U l y s s e s S . G r a n t ' ]