September 21, 2013, started out like any other day at the Westgate mall. Shoppers in search of deals strolled unaware that their lives would soon be changed forever. At midday, heavily armed militants lobbing grenades and firing indiscriminately turned the upscale shopping center in Kenya’s capital city, Nairobi, into a war zone. Security forces, caught off guard and woefully unprepared, struggled to rescue hundreds of shoppers and hunt down the assailants. By the end of a four-day siege—the worst attack on Kenyan soil since the 1998 US Embassy bombing by al Qaeda—sixty-seven people were dead and more than two hundred wounded. Al-Shabaab, a Somalia-based terrorist group that has pledged allegiance to al Qaeda, claimed responsibility for the attack.