George W. Bush's Iraq War, while duplicitous in many respects, is actually the culmination of twenty-five years of U.S. policy to ensure continued domination of the Persian Gulf and its prolific oil fields. In fact, it was a natural expression of the Carter Doctrine. Enunciated by then-President Jimmy Carter in his State of the Union speech in January 1980, the doctrine defines Persian Gulf oil as a "vital interest" of the United States that must be defended "by any means necessary, including military force." Seen in this light, Bush Jr. was merely applying the doctrine when he invaded Iraq in 2003. He's not the first. President Reagan cited it to justify U.S. intervention in the Iran-Iraq War of 1980-1988 to help ensure the defeat of Iran. President Bush Sr. invoked it to authorize military action against Iraq in 1991, during the first Gulf War. And Bill Clinton, though not explicitly citing the doctrine, adhered to its tenets.
So the use of force to ensure U.S. access to Persian Gulf oil is not a Bush II policy or a Republican policy, but a bipartisan, American policy.