What notable event occurred due to General George Armstrong Custer's actions?

General George Armstrong Custer is most notably associated with the discovery of gold in the Black Hills of South Dakota, an event that significantly escalated tensions between the U.S. government and the Native American tribes, particularly the Sioux. This discovery occurred in 1874 during an expedition led by Custer, which was supposed to be a reconnaissance mission but resulted in the unintentional violation of the Treaty of Fort Laramie. This treaty recognized the Black Hills as part of Sioux territory and prohibited any white settlers or miners from entering the area.

Following the announcement of gold, a rush of miners and settlers invaded Sioux lands, leading to a direct conflict between the U.S. government and the Sioux tribes who were determined to defend their territory. This series of events ultimately contributed to the outbreak of the Great Sioux War of 1876-77, culminating in significant battles such as the Battle of the Little Bighorn, where Custer's forces suffered a disastrous defeat.

This context reveals the profound impact of Custer’s actions in breaking the treaty and highlights the subsequent conflicts that arose as a result, making the option about breaking a treaty leading to conflict the correct response in this scenario.