Madagascar’s military has taken control of the Indian Ocean nation following the sudden departure of President Andry Rajoelina, who fled the country amid a weeks-long uprising led by Gen Z protesters and backed by mutinous soldiers. Colonel Michael Randrianirina, who led a faction of troops that defected to join the anti-government demonstrations, announced on national radio Tuesday: “We have taken power.” He declared that all state institutions were being dissolved—except the National Assembly, which had just voted to impeach Rajoelina minutes earlier. The dramatic turn came after a day of political chaos. Earlier on Tuesday, the 51-year-old president had attempted to dissolve the National Assembly by decree—a move widely seen as a last-ditch effort to cling to authority. But his...