Final answer:
Alfred Mahan believed that the navy would be weak without overseas expansion. He emphasized the need for a strong navy, the establishment of naval bases, and the construction of a canal in Central America.
Step-by-step explanation:
Alfred Mahan, a naval theorist and historian, believed that the navy would be weak without overseas expansion. In his book The Influence of Sea Power upon History, Mahan argued that sea power was essential to national greatness. He emphasized the need for a strong navy, the establishment of naval bases, and the construction of a canal in Central America to enhance the navy's reach and protect American interests.