The undisputed leader of post-revolutionary Iran and spiritual leader of millions of Shiite Muslims, Khamenei developed the nation’s nuclear program and built a once-powerful network of regional militant groups that Israel has been systematically dismantling for more than a year. His resistance to the U.S. and Israel resonated widely in the Middle East, even as it gradually fell out of step with large parts of Iran’s population, many of whom despised living under his firebrand form of theocratic governance and wanted to escape the country’s global isolation.