Complex sentence: The officer also commandeers the house for use as Union field headquarters and as courtesy it is spared, but any movable item of value (including rosaries and mattresses) are confiscated (or stolen) and larger items vandalized by the withdrawing Union troops.
Split into simpler sentences: The officer also commandeers the house for use as a Union field headquarters and as a courtesy, it is spared. However, movable items of value (including rosaries and mattresses) are confiscated (or stolen), and larger items are vandalized by the withdrawing Union troops.