In the hours following the deadly terrorist attacks of September 11, 2001, the United States government took the extraordinary step of sealing U.S. borders to traffic and trade by grounding all aircraft flying into or out of the country and imposing a lock-down on the networks of transportation and commerce that are the lifeblood of our economy and society. Given the uncertainty over what might happen next, these emergency procedures were a necessary and appropriate short-term response to the attacks. In the long run, however, a siege mentality and the construction of a fortress America are ineffective and unrealistic responses to the dangers we face. If we are to succeed in reducing our vulnerability to further terrorist attacks, we must focus our attention and resources on the gaps in intelligence gathering and information sharing that allowed nineteen terrorists to enter the United States. National security is most effectively enhanced by improving the mechanisms for identifying actual terrorists, not by implementing harsher immigration laws or blindly treating all foreigners as potential terrorists. Policies and practices that fail to properly distinguish between terrorists and legitimate foreign travelers are ineffective security tools that waste limited resources, damage the U.S. economy, alienate those groups whose cooperation the U.S. government needs to prevent terrorism, and foster a false sense of security by promoting the illusion that we are reducing the threat of terrorism.