'Know, oh Obama, that will reach America,' proclaims a black-clad militant. 'Know also that we will cut off your head in the White House, and transform America into a Muslim Province.' The militant delivers his biblical-sounding tirade flanked by comrades and standing over a kneeling Kurdish soldier who, in a gruesome climax to the video, has his head cut off. The video has emerged on the day the Islamic State threatened to kill a Japanese journalist and a Jordanian pilot within 24 hours unless a jailed female terrorist is released.