This chapter introduces the first of three foundational design questions anchoring the book: Who Leads in the Human-AI Dance? It frames leadership in human-AI collaboration as a decision strategy, determining when humans, AI, or both together should take the lead in solving problems of varying complexity and adaptability. The chapter presents a four-quadrant framework defining collaboration modes: Automated Execution, Human-in-the-Loop Operations, Machine-Augmented Decision-Making, and Expert Judgment. Through examples from national security, business, and healthcare, it illustrates how leadership must flexibly shift across these modes as conditions evolve. The concept of problem movement captures this fluidity, emphasizing that boundaries between human and AI roles blur as problems change and require reframing. Leaders must recognize these transition points and realign decision strategies to maintain contextual fit between human judgment and AI capability. By doing so, they can orchestrate collaboration that complements rather than competes. The chapter concludes by linking this first design question of who leads to the next two: How does the dance flow? and How to adapt the dance? Together, they form the foundation for navigating leadership in the age of intelligent systems.