The marriage contract had just been signed, and the festivities were in full swing. But just as close relatives of the newlyweds were emerging from an upstairs room to join hundreds of friends and family members at a Kabul wedding hall, an uninvited guest walked forward. What should have been a moment of celebration turned into a scene of unimaginable carnage, as an ISIS suicide bomber blew himself up in front of the band playing in the men’s section of the venue.