Nigeria’s former finance minister, 66-year-old Ngozi Okonjo-Iweala, becomes director-general of the Geneva-based World Trade Organization (WTO) on March 1. She is the first woman and the first African to serve in the post.

Widely known as “the Iron Lady” for her tough anticorruption crusading, Okonjo-Iweala is a competent, courageous and intelligent Harvard-trained development economist with a doctorate from the Massachusetts Institute for Technology (MIT). She spent 25 years at the World Bank, rising to vice-president, and revels in her celebrity status as a widely networked “Davos Dame”...