Final answer:
Mahan and Schurz both recognized the importance of friendly surroundings for successful defense. Mahan did not believe that the reopening of the American frontier was necessary to build an American empire.
Step-by-step explanation:
In what way do Mahan and Schurz agree? After analyzing the information, we can see that both Alfred Mahan and Carl Schurz believed that having friendly surroundings is important to successful defense. Alfred Mahan, a naval theorist, emphasized the necessity of a strong navy and overseas bases to support it, as per his 1890 publication 'The Influence of Sea Power Upon History.' Carl Schurz's ideas align with this approach, as he also recognized the importance of other factors in addition to military strength to maintain peace and avoid war. Thus, the correct answer to the question is C. Mahan and Schurz agree that friendly surroundings are important to successful defense.
Which of the following did Mahan not believe was needed to build an American empire? Alfred Mahan did not advocate for the reopening of the American frontier as a requirement for building an empire. His focuses included a strong navy, overseas bases, and strategic naval infrastructure such as a canal through Central America. Therefore, the answer is C. the reopening of the American frontier.