Robert Hopkins Chaska was caught in the middle when the U.S.-Dakota War erupted in 1862. He'd cut his hair, donned white man's clothes and taken up Christianity and farming, like many of the Dakota living along the Minnesota River in the western part of the state.

Chaska, also known as Caskedan or Caske, was 32 and lived near Thomas Williamson's Pajutazee Mission along the Yellow Medicine River near the Upper Sioux Agency. His conversion to Christianity was complete enough that he had adopted the name of Robert Hopkins, another missionary who drowned during the 1851 treaty signing at Traverse de Sioux, near St. Peter.

Williamson, his wife and sister at first refused to flee when word came up the river that some Dakota, frustrated by broken treaties and facing starvation, had attacked the Lower Sioux Agency. Williamson thought he could persuade the Dakota living up the river to resist going to war.

But two days in, Chaska urged his neighbors it was time to head east toward St. Peter and safety. Their horses had been stolen. So Chaska helped procure oxen and a cart and drove the team through Dakota lines — saving the Williamsons.

"The majority of the Dakota were against going to war, but 300 or 400 were pushing it," said Jeff Williamson, 70, a retired insurance salesman in Rosemount and the missionary's great-great grandson.

The militant Dakota urged all bands to join their campaign, convinced they could win back their homeland while white Minnesota men were down south fighting the Civil War.

"Robert evidently succumbed to this considerable pressure," according to Curtis Dahlin, a top researcher of the war and author of "The Dakota Uprising, A Pictorial History."

Chaska admitted firing a shot at the Birch Coulee standoff and being present at the final battle at Wood Lake. After the six-week war, a U.S. military commission sentenced him to hang, along with more than 300 Dakota.

"My heart aches so that I can hardly write," Aunt Jane Williamson wrote in one of many letters aimed at saving Chaska from the noose. "Surely, Caske never imbued his hands in blood."

She recalled how Chaska protected her and her brother the first night of the war. When Thomas Williamson told Chaska he could take all their sugar, molasses and meat to his home, Chaska said he'd like those goods, "but I am more anxious for your safety."

The letter writing worked. Chaska was among more than 260 Dakota whom President Abraham Lincoln and his advisers removed from the hanging list. He remained jailed in Mankato — counseling his fellow prisoners on Christianity as 38 of them were hanged the day after Christmas 1862, in what remains the nation's largest mass execution.

"Robert Hopkins in now the ruling spirit in that prison" in Mankato, noted missionary Stephen R. Riggs, who added that he preached in the prison every Sabbath.

Chaska fared better than another Chaska — a common Dakota name given to firstborn sons, like Junior. There were at least three in the Mankato prison the morning of the mass hanging.

One was sentenced to death for killing a pregnant woman. Another had been credited with protecting a doctor's wife, Sarah Wakefield, and her family during weeks of captivity. In a lethal mix-up over names, the protective Chaska was accidentally hanged.

"I doubt whether I can satisfactorily explain it," Riggs wrote later to Wakefield. He said they knew Robert Hopkins was also called Chaska and was in the prison. "We never thought of the third one, so when the name Chaska was called in the prison on that fatal morning, your protector answered it and walked out. We all regretted the mistake very much."

After the hangings, Hopkins Chaska and others spared from execution were shipped to a military prison in Iowa and then resettled on the barren plains near Crow Creek, S.D.

Even after his 1864 release, Chaska remained with the prisoners — ministering as a Presbyterian. He lived to be 78, spending time near Flandreau and Sisseton, S.D. Jeff Williamson believes he's buried near Peever, S.D., just across the Minnesota line.

In 1867, Chaska accompanied Riggs on a trip across the plains, after which the missionary wrote: "I cannot speak too highly of Hopkins. We could not well have done without him on the journey. He is equally at home chasing a buffalo or an antelope, in mending a broken wagon, and preaching the ­gospel to his people."

Curt Brown's tale on Minnesota's history appears each Sunday. Readers can send him ideas and suggestions at mnhistory@startribune.com