Which of the following was a reason why the US government asked the Five Tribes for a peace conference at Fort Smith in 1865?

During the Civil War, several of the Five Tribes made treaties with the Confederacy. At the 1865 Fort Smith conference, the U.S. government sought new agreements and required the tribes to reject those Confederate treaties. So the reason was to ask them to repudiate their treaties with the Confederacy, not to offer new western lands or reward them with annuities.

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