The theme is that of replacing a corrupt system with an equally oppressive system. The mood is one of forced optimism as the animals are determined to finish the second windmill. When they engage in the war with Frederick (after he has robbed them), he blows up the windmill. So, the mood is also one of despair and uncertainty since Napoleon (via Squealer) still continues to change the laws to suit his wishes. The latest is that ‘no animal shall drink alcohol to excess.’ Napoleon continues to spread lies about Snowball (that he was not a great hero in the battle of the cowshed) and continues his attempts to ally the animals by pitting them against others (Snowball and Frederick). For Napoleon and his retinue, the mood is surely optimistic, despite the setbacks because he and his court have all the power and privilege. For the rest of the animals, the mood is more despondent than it ever was under Jones.