How were 300 Lakota Sioux Indians, mostly women and children, armed with nothing but a couple of antique guns for hunting buffalo, slaughtered by military troops hours after they’d “surrendered”? Why were they hunted down when they fled in fear and found dead miles away?

Historians and American citizens have asked these very questions since the Wounded Knee Massacre of 1890 in South Dakota. University of Massachusetts-Amherst history professor Heather Cox Richardson thinks she’s found the answers: disengaged leaders, extreme partisanship and propagated stereotypes. Her new book, “Wounded Knee: Party Politics and the Road to an American Massacre,” shows the deadly consequences of all three in a scrupulous historical account of the politics surrounding the plight of the Sioux Indians in the late 19th century.

Richardson’s well-written narrative details the numerous Indian treaties signed and broken by the U.S. government under President Benjamin Harrison’s administration. She depicts the cycle of events and motives behind the unfair treatment of the nomadic Sioux tribes. All were forced to settle on minuscule plots of lands and relinquish their traditional hunting style of living. Many starved when they weren’t taught how to farm on the dry plains.

She also discusses the rhetoric that was used to marginalize the “uncivilized” Indians, the “savages.” According to her research, Indian agents, who were political appointees, knew very little about and even hated Indian customs and traditions — the very people with whom they were hired to work. For example, agents advised U.S. leaders to outlaw the “ghost dance,” a traditional Indian dance, and made it illegal for Indians to eat offal, or animal organs, which was an essential protein in Indians’ diets.

“The Ghost Dancers never hurt their non-Indian neighbors, and few settlers paid them much attention, but Republican political appointees did,” she wrote.

When some Indians refused to move onto reservations or give up hunting and the ghost dance, power-hungry politicians called their defiance an “act of war.” These Indians, though nonviolent, were labeled “hostile” and were eventually arrested or forced into submission, sometimes by death, according to Richardson.

But Richardson’s book goes beyond merely depicting the plight of the Sioux. It links the Indians’ tragedies directly to Washington, D.C.’s leaders, including their personalities and beliefs that influenced their actions. “The road to the massacre had begun in Washington,” Richardson wrote in one chapter. “The fate of the [Sioux] was sealed by politicians a thousand or more miles from the hills. The soldiers who pulled the triggers in South Dakota simply delivered the sentence.”

“Most scholars look at the Indians or the political system in the East,” Richardson said in an interview. “Historians often know the West but not necessarily how it plays into the East’s political system. The broad picture makes [the massacre] part of the political system — it’s not just the immediate perpetrators involved but those who put the soldiers there in the first place.”

Richardson shows how Harrison’s administration, which ultimately needed only one more Senate seat to gain a Congressional majority in the 1890 Senate election, created the state of South Dakota. Harrison did his utmost to fuel fear of the Indians and gain support by rallying against them. He mobilized 9,000 soldiers, the largest deployment of troops since the Civil War, to South Dakota to make the Indians “surrender” their way of life and settle on reservations. She said his hope was simply to gain land for settlers and their votes simultaneously.

Perhaps the greatest strength of “Wounded Knee” is Richardson’s use of primary sources. She supports her thesis with first-hand accounts and government documents, including correspondence sent by military leaders, Indian agents, Harrison and numerous players.

Although the book “leaves the connection to the reader,” Richardson expects people to notice similarities in the politics of past and politics of today in terms of war, extreme partisanship and scapegoating, she said.

Anyone interested in the history of Western expansion and the American political system will find her account more than an interesting and insightful read.