The overwhelming consensus of observers in the 1890s, and historians ever since, is that an upsurge of humanitarian concern with the plight of the Cubans was the main motivating force that caused the war with Spain in 1898. McKinley put it succinctly in late 1897 that if Spain failed to resolve its crisis, the United States would see “a duty imposed by our obligations to ourselves, to civilization and humanity to intervene with force."Intervention in terms of negotiating a settlement proved impossible—neither Spain nor the insurgents would agree. Louis Perez states, "Certainly the moralistic determinants of war in 1898 has been accorded preponderant explanatory weight in the historiography."
By the 1950s, however, American political scientists began attacking the war as a mistake based on idealism, arguing that a better policy would be realism. They discredited the idealism by suggesting the people were deliberately misled by propaganda and sensationalist yellow journalism. Political scientist Robert Osgood, writing in 1953, led the attack on the American decision process as a confused mix of "self-righteousness and genuine moral fervor," in the form of a "crusade" and a combination of "knight-errantry and national self- assertiveness."
