When Forrest's cavalry brigade is at 2 SP in strength and he is eliminated through general battle death, does only 1 SP go to the turn track and the other stay in the space, or do both SP go to the turn track?
Both go to turn track. However you can always choose to take those as casualties after you know the Forrest is dead. Its rare to see SPs from cavalries in turn track because of that. The usual reasons are Ambush or Forrest dying while the army took 1 damage & he was at 2.