By Norimitsu Onishi and Jeffrey Moyo Nov. 21, 2017 HARARE, Zimbabwe — Robert Mugabe, who has ruled Zimbabwe since independence in 1980, resigned as president on Tuesday shortly after lawmakers began impeachment proceedings against him, according to the speaker of Parliament. The speaker of Parliament read out a letter in which Mr. Mugabe said he was stepping down “with immediate effect” for “the welfare of the people of Zimbabwe and the need for a peaceful transfer of power.” Parliament erupted into cheers and jubilant residents poured into the streets of Harare, the capital. It seemed to be an abrupt capitulation...