United States foreign policy changed in some very noticeable ways after September 11, 2001. In other ways, foreign policy after 9/11 has remained much the same.

When George W. Bush assumed the presidency in January 2001, his major foreign policy initiative was the creation of a "missile shield" over parts of Europe. In theory, the shield would give added protection if North Korea or Iran ever launched a missile strike.

In fact, Condoleezza Rice, then the head of Bush's National Security Council, was slated to give a policy speech about the missile shield on September 11, 2001.

Focus on Terror

Nine days later, on September 20, 2001, in a speech before a joint session of Congress, Bush changed the direction of American foreign policy. He made terrorism its focus.

"We will direct every resource at our command -- every means of diplomacy, every tool of intelligence, every instrument of law enforcement, every financial influence, and every necessary weapon of war -- to the destruction and to the defeat of the global terror network," Bush said.

The speech is perhaps best remembered for this remark. "[W]e will pursue nations that provide aid or safe haven to terrorism," said Bush. "Every nation in every region now has a decision to make: Either you are with us or you are with the terrorists."

Preventive Warfare, Not Preemptive

The most noticeable change in U.S. foreign policy is its focus on preventive action, not just preemptive action.

This is also known as the Bush Doctrine.

Nations often use preemptive strikes in warfare when they know that an enemy action is eminent.

When the U.S. invaded Iraq in March 2003, however, it broadened its policy to include preventive warfare. The Bush administration told the public (erroneously) that Saddam Hussein's regime had nuclear material and would soon be able to produce atomic weapons. Bush vaguely tied Hussein to Al Qaeda (again erroneously), and he said the invasion was, in part, to prevent Iraq from supplying terrorists with nuclear weapons. Thus, the Iraqi invasion was to prevent some perceived -- but not clearly evident -- event.

Humanitarian Assistance

U.S. humanitarian assistance has become more subject to foreign policy demands, and in some cases it has become militarized. Independent Non-Government Organization (NGOs) working through USAID (a branch of the U.S. State Department) have typically delivered worldwide humanitarian aid independently of American foreign policy. However, as Elizabeth Ferris reported in a recent Brookings Institution article, U.S. military commands have begun their own humanitarian assistance programs in areas where they are conducting military operations. Therefore, army commanders can leverage humanitarian assistance to gain military advantages.</>

NGOs have also increasingly fallen under closer federal scrutiny, to ensure that they comply with U.S. anti-terrorism policy. This requirement, says Ferris, "made it difficult, indeed impossible, for U.S. humanitarian NGOs to claim that they were independent of their government's policy." That, in turn, makes it more difficult for humanitarian missions to reach sensitive and dangerous locations.

Questionable Allies

Some things, however, have not changed. Even after 9/11, the U.S. continues its tendency to forge questionable alliances.

The U.S. had to secure Pakistan's support before invading neighboring Afghanistan to fight the Taliban, which intelligence said was an Al Qaeda supporter. The resulting alliance with Pakistan and its president, Pervez Musharraf, was awkward. Musharraf's ties with the Taliban and Al Qaeda leader Osama bin Laden were questionable, and his commitment to the War on Terror seemed halfhearted.

Indeed, in early 2011, intelligence revealed that bin Laden was hiding in a compound in Pakistan, and apparently had been for more than five years. American special ops troops killed bin Laden in May, but his mere presence in Pakistan cast more doubt on that country's commitment to the war. Some members of Congress soon began calling for an end to Pakistani foreign aid.

The U.S. has also found an uneasy ally in Hamid Karzai, president of post-invasion Afghanistan. Karzai is known to be corrupt, but he tolerates American presence in Afghanistan.

Those situations are reminiscent of American alliances during the Cold War. The United States supported such unpopular leaders as the Shah of Iran and Ngo Dinh Diem in South Vietnam, simply because they were anti-Communist.

War Weariness

George W. Bush warned Americans in 2001 that the War on Terror would be long, and its results might be hard to recognize. Regardless, Bush failed to remember the lessons of the Vietnam War and to understand that Americans are results-driven.

Americans were encouraged to see the Taliban virtually driven from power by 2002, and could understand a brief period of occupation and state-building in Afghanistan.

When the invasion of Iraq pulled resources away from Afghanistan, allowing the Taliban to become resurgent, and the Iraqi war itself became one of seemingly unending occupation, Americans became war-weary. When voters briefly gave control of Congress to Democrats in 2006, they were in fact rejecting Bush's foreign policy.

That public war weariness effects the Obama administration as the current president wrestles with withdrawing troops from Iraq and Afghanistan as well as allocating funds for other military ventures, such as America's limited involvement in the Libyan civil war.