When Napoleon and Snowball disagree on the windmill project, the hens become involved because of their importance in providing eggs. Napoleon uses their desire to hatch more chicks as a distraction and bribes the hens with extra feed to convince them to vote in his favor. They subsequently support Napoleon during the vote, contributing to Snowball's expulsion.
Napoleon manipulates the hens, who are not directly involved in the farm's main activities or the intellectual debates between the pigs. Their limited understanding and susceptibility to manipulation highlight Napoleon's cunning strategies to secure power and suppress any challenge to his authority.
As the story progresses, Napoleon's control tightens, and the hens become increasingly marginalized and oppressed. They do not see any improvement in their living conditions or rights, despite the revolution's initial promise of equality among all animals.
Overall, the hens' involvement in the power struggles and their subsequent fate illustrate Napoleon's ability to exploit and control the vulnerable members of the animal society in "Animal Farm."