Entering the 1930s, demands for transportation from Japan to China increased rapidly due to the Manchurian Incident and Sino-Japanese war, increasing the amount of traffic on the Tokaido Main line and Sanyo Main line as well.
1930年代に入ると満州事変・日中戦争などによる日本から中国へ向かう輸送需要の激増で、東海道本線・山陽本線の輸送量も増大した。