They had been doing it for four months.

The people who left that night were taking a tremendous risk.

The plains north of the Bear Paw Mountains were open country where mounted pursuit could be effective.

The cold was severe.

They were going without most of their horses.

They would have to cover roughly forty miles to the border on foot or with very limited mounts.

And they did.

The forty miles that had been unreachable in the five days of the siege — because the army held the horses and controlled the approaches — were covered in the hours after the decision was made.