Answer:
Indian Wars took place during the second half of the 19th century because of the American expansionism, that encouraged white settlers to create towns and cities in territories belonging to Indian tribes, who considered this an intrusion in their ancestral territories.
Step-by-step explanation:
These wars, which extend from colonial times to the Wounded Knee Massacre and the definitive establishment of the US border in 1890, were generally resolved with the conquest of native peoples and their forced cultural assimilation or their forced location in reserves. The number of Indians fell to less than half a million in the 19th century due to infectious diseases, conflicts with Europeans, inter-tribal wars, assimilation, migration to Canada and Mexico, and declining birth rates. The main cause was infectious diseases transmitted by European explorers and traders.
The Indians in the United States were (and still are) a set of different cultures with their own stories. Throughout the various wars of indigenous people against settlers in Europe and the United States, those did not form a single unified side or fight for the same causes. Living in societies organized in various ways, Native Americans normally made their decisions about war and peace at the local level, although sometimes they could fight as part of formalized alliances, such as the Iroquois confederation, or in temporary confederations inspired by leaders like Tecumseh.