Final answer:
The leaders of pan-tribal sodalities among Native American tribes functioned as political guides and spiritual leaders, providing governance and maintaining religious practices while facing cultural suppression by American expansion policies.
Step-by-step explanation:
The leaders of pan-tribal sodalities among Native American tribes of the Great Plains during the 18th and 19th centuries primarily served two social functions: political guidance and spiritual leadership. As both war chiefs and peace chiefs, these leaders played critical roles in the governance of their tribes. The war chiefs were often younger and were preparing for eventual leadership as peace chiefs, which allowed for the continuity and stability of political systems. Even as Plains groups faced immense pressures from American expansion and policies aimed at assimilation, chiefs also were pivotal in spiritual activities such as the Sun Dance, maintaining religious and cultural practices central to their communities.
Two-spirit individuals in these societies also held important roles and were valued for their unique contributions and spiritual insight, serving as healers, leaders, and intermediaries. Even in the wake of harmful civilization policies, which enforced individual land ownership and suppressed Native culture and traditions, these leaders strived to sustain their peoples' way of life and sovereignty.