A series of meetings occurred in the spring of 1999, involving Khalid Sheikh Mohammed, Osama bin Laden, and his deputy Mohammed Atef. Bin Laden recommended four individuals for the plot, including Nawaf al-Hazmi, Khalid al-Mihdhar, Walid Muhammad Salih Bin 'Attash (Khallad), and Abu Bara al-Taizi. Al-Hazmi and al-Mihdhar were both Saudi citizens, thus making it simple for them to obtain U.S. visas. Khallad and al-Taizi were both Yemeni citizens, thus not able to easily obtain visas to the United States. The two Yemenis were assigned for the Asia component of the plot. When Mohamed Atta and other members of the Hamburg cell arrived in Afghanistan, bin Laden was involved in selecting them for the plot, and assigning Atta to be the leader.