Terrorism against Americans and US interests has increased in recent decades. Major terror attacks included the 1988 bombing of Pan Am flight 103, the 1993 World Trade Center bombing, the 1995 Oklahoma City bombing, attacks by the Unabomber in the 1990s, the 1996 bombing of a US military base in Dhahran, and the 1998 bombings of US embassies in Kenya and Tanzania. The 9/11 attacks in 2001 targeted the World Trade Center towers and the Pentagon. Osama bin Laden began his career as a terrorist in Afghanistan. Al-Qaeda declared war on the US and is difficult to size as its membership is hard to verify. Notable al-Qaeda attacks include 9/11, the 2000