Answer:
Step-by-step explanation:
The phrase "its 'controlling' (not simply its 'declared') policy was the maintenance of peace in the Pacific" means that the policy being referred to is not just something that is written down or stated publicly, but it is the actual policy that guides the actions of the country. In this context, it suggests that the policy of maintaining peace in the Pacific is not just something that is talked about, but it is the primary guiding principle that informs all decisions and actions taken by the country.