Final answer:
The international response to German aggression up to 1938 was mostly unsuccessful, as evidenced by the policy of appeasement at the Munich Conference and the lack of a united resistance among powerful nations.
Step-by-step explanation:
The international response to German aggression leading up to 1938 could be considered mostly unsuccessful. This stance is rooted in the events that transpired during that time which include the policy of appeasement as adopted by European democracies, the annexation of Czechoslovakia by Germany, and the lack of a conclusive stance from world powers on the growing threat of fascism.
The Munich Conference of September 1938, where Britain and France agreed not to interfere with Hitler's plans in Czechoslovakia, is a highlight of this unsuccessful response. This decision was influenced by factors such as the uncertainty of military preparedness, political conservatives in England and France favoring Germany over the Soviets, and the United States' isolationist policy diminishing hopes for aid. Furthermore, the failure to address the concerns from World War I and pre-existing tensions in Europe allowed Germany to exploit the situation further, ultimately exacerbating international relations and paving the way for further expansion.
Nevertheless, the response wasn't a complete failure, as there were attempts to curb German aggression. However, these efforts largely failed due to competing interests, underestimation of Hitler's ambitions, and the absence of a united front against aggression. This led to the disintegration of collective security and a strengthened resolve by Germany to continue its expansionist agenda which had been peaceful so far and included mostly people of German descent.