The emergence of geopolitical-mindedness was a major phenomenon of American intellectual and diplomatic history. The consciousness of power and the readiness to consider war as an instrument of national policy such a realist response to world affairs was to have a profound impact on the way the American people viewed external events. Throughout 1936, the isolationist thrust of American foreign policy did not change, reconfirmed by the Neutrality Act of that year, which extended mandatory neutrality to the extension of loans and credits to belligerents. The State Department encouraged Americans to evacuate from the interior of China and discouraged ships carrying aircraft and other arms for China from reaching their destination lest they should be intercepted by the Japanese navy. President Theodore Roosevelt was particularly eager to strengthen American naval power and fully endorsed the Vinson Naval Expansion Act of May, providing for a new program of naval rearmament.