Men are forced to grow beards. Women can’t leave home without a male relative. Music, movies and watching sports on TV are banned. Limbs are chopped off as punishment, and executions by stoning have become a public spectacle…

“Al-Shabab is copying exactly whatever the Taliban was doing in the late 1990s, because they think the strategies the Taliban employed in Afghanistan were successful,” said Vahid Mujdeh, the Afghan author of a book on the Taliban. “There is no doubt that the Taliban are like heroes for al-Shabab.”

U.S. and other security officials worry about another common thread: Both the Taliban and al-Shabab have links to al-Qaida.