Final answer:
Naval intelligence involves the provision and maintenance of a Navy, making rules for the government and regulation of the land and naval forces, and protecting the nation from threats through intelligence and counterintelligence services.
Step-by-step explanation:
The nature and purpose of Naval intelligence in the context of defense policy is to provide and maintain a Navy, make rules for the government and regulation of the land and naval forces, and provide for calling forth the Militia to execute the laws of the Union, suppress insurrections, and repel invasions. In terms of intelligence services, the nature is to use intelligence services to defeat threats, while the purpose is to protect the nation from internal threats through counterintelligence measures.