The transcontinental railroad was also entering the calculation.

The Union Pacific was building west through Kansas and Nebraska, and when it reached Wyoming, it would provide an alternative route to Montana that avoided the Powder River Country entirely.

If the railroad could get passengers and freight to Montana, the Bozeman Trail’s entire economic justification would disappear.

Why continue fighting over a road that would soon be obsolete?

The combination of these factors — military failure on the ground, political pressure in Washington, the economic logic of the railroad — created the conditions for a policy reversal.

The question was how to frame the retreat in terms that were politically manageable.