[citation needed] In the second half of the 19th century, under strong military and diplomatic pressure, and suffering from an internal crisis that led to the collapse of the Bakufu, Japan opened its ports, and subsequently the nation, to commerce with the outside world and reform that sought to respond vigorously to the challenges of modern industrial polities, as they were remarked on by Japanese observers in the United States and Europe.
Just as ukiyo-e were first reimported back into Japan from Paris museums and private European collections after World War 1, less tangible aspects of the cultural past were newly rediscovered by Japanese visitors in Europe.
The Taishō period marked a slightly more 'liberal' turn, as the pendulum swung towards a renewed interest in the Western model ("Japan must undergo a second birth, with America as its new mother and France as its father").
With the crisis of 1929 and the concomitant depression of the 1930s, militarism gained the upper hand in this era of the 'dark valley' (暗い谷間, kurai tanima), and nationalistic ideologies prevailed over all attempts to keep alive the moderate traditions of liberal modernity.
[10] The frequency of these chronic transitional upheavals engendered a remarkable intensity of debate about national directions and identity (国民性 kokuminsei; 民族性 minzokusei), whose complexity over time renders a synthetic judgment or bird's-eye view of the literature in question rather difficult.
[11] Some scholars cite the destruction of many Japanese national symbols and the psychological blow of defeat at the end of World War II as one source of nihonjinron's enduring popularity, although it is not a uniquely 20th century phenomenon.
Scholars such as Hisao Ōtsuka, a Weberian sociologist, judged Japan with the measure of rational individualism and liberal democracy that were considered ideals in the U.S. and Western European nations back then.
Dale, for example, characterizes nihonjinron as follows: First, they implicitly assume that the Japanese constitute a culturally and socially homogeneous racial entity, whose essence is virtually unchanged from prehistoric times down to the present day.
[14]The emphasis on ingroup unity in nihonjinron writings, and its popularization during Japan's period of military expansion at the turn of the 20th century, has led some Western critics to brand it a form of ethnocentric nationalism.