During the 1930s, the German and Austrian Alpine Society sponsored three mountaineering-scientific expeditions to the Peruvian Andes, focusing especially on the Cordillera Blanca and adjacent valley known as the Callejón de Huaylas. They climbed mountains, conducted scientific studies, produced detailed maps, explored the highlands, and interacted with Peruvian intellectuals. Similar German expeditions went to Asia, Africa, and elsewhere in South America during this decisive period for the Nazi empire. This essay analyzes the writings and publications of the German and Austrian mountaineer-scientists who went to Peru, especially the Austrian leader Hans Kinzl, as well as examining government documents, technical reports, tourism publicity, diplomatic correspondence, and travel accounts to understand how Peruvian policy makers, engineers, scientists, intellectuals, tourism boosters, regional authorities, urban-based ruling classes, and rural residents in the mountains interacted with the European mountaineer-scientists during and after their expeditions. Most Peruvian groups initially welcomed the foreign mountaineer-scientists, using their activities to pursue their own agendas during the 1930s and 1940s. By the 1960s, however, many had become opposed to foreign mountaineers and scientists “intervening” in the Andes. World War II, natural disasters, the weak nation-state, coast-sierra divisions, growing Peruvian expertise in science and engineering, and the rise of an Andean tourism economy influenced how Peruvians perceived and interacted not only with the foreign mountaineer-scientists, but also with the Andean alpine landscape. Moreover, the dynamic physical environment also shaped historical processes: from science and engineering to landscape perceptions, tourism economies, national development, and international relations.