Michelle Bachelet, President of Chile, is one of Latin America’s most prominent leaders. A moderate Socialist who has pledged to combine pursuit of the country’s free-market policies with social measures to narrow the gap between rich and poor, her actions and pronouncements are of special interest to the outside world at a time of turbulent political change elsewhere in the region.

Bachelet’s life and political career have been significantly shaped by Chile’s troubled recent past. Detained and roughed up in 1975—two years after the late General Pinochet came to power in a military coup—she spent a period in exile, first in Australia then in the German Democratic Republic (the former East Germany), before returning to Chile in 1979. Like others on the left, she was active in the battle to restore democracy to the country in the late 1980s.

A trained surgeon who has also studied military strategy, Bachelet first came to national political prominence as health minister in the government of her predecessor Ricardo Lagos, where she initiated an in-depth review of Chile’s health care system. Subsequently appointed the minister of...