With a perspective sharpened by knowledge of post-War events, historians of American religion have pointed to underlying conflicts and discrepancies which belied the idealistic confidence of the pre-War era. Economic turmoil, urbanization, the rise of historical criticism and evolutionary theory, the issue of liberalism versus revivalism—all these potentially disruptive elements lay beneath the assured facade of pre-War American Protestantism. Sydney Ahlstrom has attributed the foreign missions boom of the era to the churches' desire to avoid confrontation on these issues: "crusades of diverse sorts were organized, in part, it would seem, to heal or hide the disunity of the churches." Robert Handy has seen the mission enterprise as an extension of the voluntaryism of the 1830s—a means for cooperative Protestant action in society without confrontation on particular denominational differences. Handy, like Ahlstrom, has pointed to the dangers which were inherent in sublimation of theological and social controversy under activist crusades: "The possibility of a greater sense of self-criticism, which might have come out of a more open confrontation of the parties, was largely suppressed, in considerable measure because of the necessities of the missionary consensus. .