Her deck, once red with heroes' blood, Where knelt the vanquished foe, When winds were hurrying o'er the flood, And waves were white below, No more shall feel the victor's tread, Or know the conquered knee; -- The harpies of the shore shall pluck The eagle of the sea! Oh, better that her shattered hulk Should sink beneath the wave; Her thunders shook the mighty deep, And there should be her grave; Nail to the mast her holy flag, Set every threadbare sail, And give her to the god of storms, The lightning and the gale. Which of these BEST describes a theme of this poem?