This pamphlet, What is Japan fighting for? : the truth about the Sino-Japanese conflict and several others like it were printed by other Japanese Associations and Chambers of Commerce at the behest of the Foreign Ministry. The Japanese Association of San Francisco printed up between 50 to 60000 pamphlets in 1937, as did Japan Associations in Chicago and NYC and other cities in the West coast. The overarching rationale for these pamphlets was two-fold. Firstly, it helped to shore up Japan's position among the Issei (first generation) community. This group of immigrants had become a relatively prosperous community in the US, often in the teeth of serious discrimination, and often made remittances back to the Home Islands. The hope was that this community would use their wealth and disposable income to help sustain the Japanese war effort. This could involve sponsorship of families with a soldier deployed in China, the sending of care packages with American luxuries like razor blades to the IJA and IJN troops, or contributions directly to Japan's war coffers. While these contributions were a drop in the bucket for the Japanese war effort, this type of military boosterism was quite common in the 1930s and often manifested itself in symbolic gifts for the war effort. For example, the Japanese Association of Pasadena in 1938 contributed enough funds to but the IJA a liaison aircraft and the IJN a carrier-based aircraft.

The second reason for these types of pamphlets was what today would fall under the moniker "public diplomacy." Although American public opinion was firmly against American intervention in China, most Americans blamed the Japanese for the outbreak of hostilities. The pamphlets, along with other media like the Japanese-American press, public lectures, and English-language radio broadcasts from NHK shortwave sought to redress this pro-Chinese slant of American public opinion. The Domei News Agency and the Foreign Ministry sought to control the story coming out of China and portray Japanese actions in the best possible light.

In hindsight, this boosterism and public diplomacy was a disaster for the Japanese-American community as it gave an additional pretext for internment. Such boosterism followed already established patterns set by the First Sino-Japanese War and the Russo-Japanese War. Additionally, the US government's denial of naturalization rights to Issei fostered this connection to their homeland; amidst this boosterism, many Issei noted with consternation that Nisei (second-generation) did not share their enthusiasm for Japan's war. The Nisei-dominated Japanese-American Citizens League often looked askance at their elders' support for Japan and some of its leaders cooperated with the FBI as early as 1939 in investigations of some of the more nationalistic Issei individuals. But such cooperation stood for naught after Pearl Harbor and both generations became potentially dangerous aliens in the eyes of the US government.

Source

Ichioka, Yuji, and Gordon H. Chang. Before Internment Essays in Prewar Japanese American History. Stanford, Calif: Stanford Univ. Press, 2006.