Al-Mihdhar was born on May 16, 1975, in Mecca, Saudi Arabia to a prominent family, related to the Quraysh tribe of Mecca. Little is known about his life before the age of 20, when he and childhood friend Nawaf al-Hazmi went to Bosnia and Herzegovina to fight with the mujahideen in the Bosnian War. After the war, Mihdhar and Hazmi went to Afghanistan where they fought alongside the Taliban against the Northern Alliance, and al-Qaeda would later dub Hazmi his "second in command". In 1997, Mihdhar told his family that he was leaving to fight in Chechnya, though it is not certain that he actually went to Chechnya. The same year, both men attracted the attention of Saudi Intelligence, who believed they were involved in arms smuggling, and the following year they were eyed as possible collaborators in the 1998 United States embassy bombings in East Africa after it emerged that Mohamed Rashed Daoud Al-Owhali had given the FBI the phone number of Mihdhar's father-in-law; 967-1-200578, which turned out to be a key communications hub for al-Qaeda militants, and eventually tipped off the Americans about the upcoming Kuala Lumpur al-Qaeda Summit.
In the late 1990s, Mihdhar married Hoda al-Hada, who was the sister of a comrade from Yemen, and they had two daughters. Through marriage, Mihdhar was related to a number of individuals involved with al-Qaeda in some way. Mihdhar's father-in-law, Ahmad Mohammad Ali al-Hada, helped facilitate al-Qaeda communications in Yemen, and in late 2001, Mihdhar's brother-in-law, Ahmed al-Darbi, was captured in Azerbaijan and sent to Guantanamo Bay on charges of supporting a plot to bomb ships in the Strait of Hormuz.
Selection for the attacks
In Spring 1999, al-Qaeda founder Osama bin Laden committed to support the 9/11 attacks plot, which was largely organized by prominent al-Qaeda member Khalid Sheikh Mohammed. Mihdhar and Hazmi were among the first group of participants selected for the operation, along with Tawfiq bin Attash and Abu Bara al Yemeni, al-Qaeda members from Yemen. Mihdhar, who had spent time in al-Qaeda camps in the 1990s, was known and highly regarded by Bin Laden. Mihdhar was so eager to participate in jihad operations in the United States that he had already obtained a one-year B-1/B-2 (tourist/business) multiple-entry visa from the consulate in Jeddah, Saudi Arabia, on April 7, 1999, one day after obtaining a new passport. Mihdhar listed the Los Angeles Sheraton as his intended destination.
Once selected, Mihdhar and Hazmi were sent to the Mes Aynak training camp in Afghanistan. In late 1999, Hazmi, Attash and Yemeni went to Karachi, Pakistan to see Mohammed, who instructed them on Western culture and travel; however, Mihdhar did not go to Karachi, instead returning to Yemen. He was known as Sinaan during the preparations.