Ratzel's writings coincided with the growth of German industrialism after the Franco-Prussian war and the subsequent search for markets that brought it into competition with England. His writings served as welcome justification for imperial expansion. Influenced by Mahan, Ratzel wrote of aspirations for German naval reach, agreeing that sea power was self-sustaining, as the profit from trade would pay for the merchant marine, unlike land power. Haushofer was exposed to Ratzel, who was friends with Haushofer's father, a teacher of economic geography, and would integrate Ratzel's ideas on the division between sea and land powers into his theories by saying that only a country with both could overcome the conflict. Here, Hitler diverged with Haushofer's writings in consigning Germany to sole pursuit of land power.