Approximately 20,000 foreigners have traveled to Syria to join in jihad with various terrorist organizations, including the Islamic State. Experts estimate about 3,000 recruits are from Western nations -- and up to 150 are from the United States.
In their latest video released Monday, Boko Haram leader Abubakar Shekau vowed to defeat the military force launched by the African Union to take down the militant group. The video was the first released by the group to include images of ISIS leader Abu Bakr al-Baghdadi.
"People committed terrible deeds in the name of Christ," Obama says.