"immediate surrender really is the first option for you guys, isn't it? :-)"
If you're going to lose anyway, and you're wrong in the first place, making a deal is common sense.
Fighting to the death...and getting predictably killed...is pointless.
How long ago did the Santee fail?
The Santee's history is Indian history in microcosm. In the early 1850's, they made a stupid land deal trading large chunks of real estate for money. When, as usual, the Indian agents started exploiting the Indians, and the Indians discovered that the hunting rights they retained were no use when all the game had been killed off by agrarian settlement, they rebelled in an extremely vicious way during the Civil War, killing approximately 750 settlers, mostly women and children. The rebellion was quashed after a couple of months, and despite the whining of contemporary members of the tribe, reprisals were extremely mild, considering the reports of what the Santee did - decapitating children and using their heads as footballs, etc.; 33 Santee were executed, the rest having had their death sentences commuted by Abraham Lincoln. They were, however, removed from Minnesota, Congress having abrogated all treaties following the massacre (which they were entitled to do) and the Santee were dispersed on three or four reservations in the Dakotas and northern Nebraska.