Final answer:
The Indian tribes' relocation to Indian Territory during the 1830s was primarily due to forced removal as a result of the Indian Removal Act of 1830.
Step-by-step explanation:
The primary reason for the Indian tribes' relocation to Indian Territory during the 1830s was forced removal. This was a result of the Indian Removal Act of 1830, passed by Congress, which forced Native Americans to move west of the Mississippi River. The act was driven by the desire to open up land for White settlement and to expand White dominance over fertile soil and resources.