defense spending increased from $306 billion in 2001 (2.9% gdp) to $612 billion in 2008 (4.2% gdp). the invasion of afghanistan following the 9/11 attack on the world trade center in 2001, along with the 2003 invasion of iraq, added significantly to defense spending. the congressional research service estimated that congress approved $1.6 trillion during the fy2001-fy2014 periods for "military operations, base support, weapons maintenance, training of afghan and iraq security forces, reconstruction, foreign aid, embassy costs, and veterans’ health care for the war operations initiated since the 9/11 attacks." roughly half this amount, $803 billion, was approved for the fy2001-2008 period of the bush administration.