Harvard Business Review published its first issue 100 years ago with a mission to help leaders put the best management thinking into practice. To mark our centennial, we asked eight current and former CEOs from some of the world's top companies to describe the ideas that have propelled their own careers and organizations. Stephane Bancel, the CEO of Moderna, on planning from the future back; Anish Shah, CEO of Mahindra, on purpose-driven strategy; Roz Brewer, CEO of Walgreens Boots Alliance, on listening as a leader; Nicolas Hieronimus, CEO of L'Oreal, on global vision with local execution; Joey Wat, CEO of Yum China, on continuous innovation; Mo Ibrahim, former CEO of Celtel, on inclusive capitalism; Ignacio Galan, CEO and chairman of Iberdrola, on transparent sustainability reporting; Indra Nooyi, former CEO of PepsiCo, on performance with purpose. As we at HBR look to the future, we recommit to our mission of helping leaders build a better world for customers, employees, partners, and communities.

Back in the late 1990s Ibrahim, who was running a software and consulting company in the UK, regularly worked with big telecom companies. He began asking them why they were ignoring the huge opportunities to develop mobile communications in Africa, especially in countries where licenses would be free. The telecom executives who were his clients simply saw Africa as too unknown and too risky. One of them cited Idi Amin as a barrier--but Amin had been gone from Uganda for 15 years. Convinced that the potential market was too big to pass up, Ibrahim decided to develop it himself. He began with just five employees and initial funding from his consulting firm, and subsequently had to spend a significant amount of time raising capital--$300 million during the first five years. To establish credibility, he recruited an experienced and respected board and instituted rules to prevent bribery and corruption. The company began in Uganda and a few other countries where the pent-up demand was almost overwhelming. In Gabon, for example, customers actually knocked down the door in one of its offices trying to get in. "That's how badly people wanted to make phone calls," Ibrahim writes. The challenges he faced in meeting that demand were infrastructural as well as political and cultural: Some places lacked roads, so helicopters had to move the heavy equipment. The company had to supply its own electricity and water and to refill its batteries and generators every day. Nevertheless, Ibrahim succeeded in building a large company and creating an even larger economy to support it. When Celtel was sold to Zain, in 2005, it was operating in 15 African countries under licenses that covered more than a third of the continent's population.