It’s not clear that Emwazi’s death, if confirmed, would have an important effect on the Islamic State’s strength or its hostage operations. But the killing of a well-known militant who embodies the brutal tactics of the militant group, and its allure to Westerners, would be a symbolic blow.

Since it launched airstrikes over Iraq and Syria last year, the United States has killed a number of militants it has described as senior members of the Islamic State. But if Emwazi’s death is confirmed, he would be by far the best-known militant to have been slain. The group’s leader, Abu Bakr al-Baghdadi, remains at large.

Despite more than a year of U.S. and allied efforts against the Islamic State, the group remains a potent force that controls a wide swath of territory across Iraq and Syria.

have suggested she was killed by the Islamic State.For more than a year, Western officials have sought to determine the whereabouts of Emwazi, who is thought to have made his way to Syria around 2012 and later joined the Islamic State.Now in his mid-20s, Emwazi was born in Kuwait but grew up in a London family and studied computer programming before becoming radicalized. Emwazi was described by those who knew him before his militant days as a polite, fashionable young man who adhered to his Islamic faith.Friends say his path toward militancy appears to have begun after his graduation from the University of Westminster, when he and several friends planned a trip to Africa, ostensibly to go to Tanzania for a safari. He was detained by authorities after arriving there and deported to Amsterdam, where he claimed to have been questioned by MI5, Britain’s domestic security agency, and accused of having tried to travel to Somalia.Somalia is home to another militant group, al-Shabab. Emwazi denied seeking to join al-Shabab.Emwazi later moved to his native Kuwait, where he worked for a computer company, but he returned to Britain several times. In 2010, he was detained by British authorities and barred from leaving the United Kingdom. It is not known how or when he reached Syria.Emwazi and the other so-called Beatles appeared to grow in stature and influence within the Islamic State over time. The group has used the detention and killing of foreign hostages, which has drawn intense attention in the West, as a tool for highlighting its power and goals.In an attempt to accelerate the isolated successes that have occurred in recent months, the Obama administration late last month announced measures that will expand U.S. military involvement in both countries. For the first time, the Pentagon will position a small number of Special Operations troops on the ground in Syria.