There is some disagreement among scholars about how widespread warfare was in pre-Columbian America, but there is general agreement that war became deadlier after the arrival of the Europeans and their firearms. The South or Central American infrastructure allowed for thousands of European conquistadors and tens of thousands of their Indian auxiliaries to attack the dominant indigenous civilization. Empires such as the Incas depended on a highly centralized administration for the distribution of resources. Disruption caused by the war and the colonization hampered the traditional economy, and possibly led to shortages of food and materials. Across the western hemisphere, war with various Native American civilizations constituted alliances based out of both necessity or economic prosperity and, resulted in mass-scale intertribal warfare. European colonization in the North American continent also contributed to a number of wars between Native Americans, who fought over which of them should have first access to new technology and weaponry—like in the Beaver Wars.