In September 2002, the Bush administration published its National Security Strategy, which articulated a dramatic change in its foreign policy outlook after the 9/11 terrorist attacks. The new strategy declared that "we are menaced less by fleets and armies than by catastrophic technologies falling into the hands of the embittered few."
The new strategy attracted criticism at home and abroad for its excessive rhetoric about preemptive military strikes and the promotion of American primacy.
Critics pointed out that the practice of preemption is not new, but turning it into a doctrine weakens international norms and encourages other countries to engage in risky actions. Similarly, they argued, American primacy is a fact, but there is no need for rhetoric that rubs other peoples' faces in it.
Notwithstanding such flaws, the new Bush strategy responded to the deep trends in world politics illuminated by the events of Sept. 11, 2001. And that response was correct in many ways because transnational terrorism and weapons of mass destruction are the greatest threats we face.
But what the administration has not yet sorted out is how to go about implementing the new approach to these threats. The US has done far better on identifying the ends than the means.
The means the administration has chosen have focused too heavily on "hard power," such as military force and economic suasion, and has not taken enough account of "soft power," such as persuading others to want the outcomes it wants. And that is a mistake, because terrorists stand to gain recruits and popular support if the US underestimates the importance of soft power.
Indeed, by acting impatiently and failing to develop a broad coalition for the invasion of Iraq, the Bush administration undercut its own strategy and helped Al Qaeda gain new recruits throughout the Islamic world. Recent polls show that after the Iraq war, more people in "friendly" countries such as Jordan and Pakistan are attracted to Osama bin Laden than to George W. Bush.
Hard power can rest on tangible inducements (carrots), or threats (sticks), to get others to change their position. But sometimes governments can get the outcomes they want without threats or payoffs. The indirect way to a desirable outcome has been called the second face of power. A country may obtain outcomes it wants in world politics because other countries want to follow it, admiring its values, emulating its example, aspiring to its level of prosperity and openness. In this sense, it is also important to set the agenda and attract others in world politics.
Soft power co-opts people rather than coerces them. It rests on the ability to set the agenda or shape the preferences of others.
It is a mistake to discount soft power as just a question of image, public relations, and ephemeral popularity. It is a form of power - a means of pursuing national interests.
When America discounts the importance of its attractiveness to other countries, it pays a price. When US policies lose their legitimacy and credibility in the eyes of others, attitudes of distrust tend to fester and further reduce its leverage.
The manner with which the US went into Iraq undercut American soft power. That did not prevent the success of the four-week military campaign, but it made others less willing to help in the reconstruction of Iraq and made the American occupation more costly in the hard-power resources of blood and treasure.
Because of its leading edge in the information revolution and its past investment in military power, the US probably will remain the world's single most powerful country well into the 21st century. But not all the important types of power come from the barrel of a gun.
Hard power is relevant to getting desired outcomes, but transnational issues such as climate change, infectious diseases, international crime, and terrorism cannot be resolved by military force alone.
Soft power is particularly important in dealing with these issues, where military power alone simply cannot produce success, and can even be counterproductive.
America's success in coping with the new transnational threats of terrorism and weapons of mass destruction will depend on a deeper understanding of the role of soft power and developing a better balance of hard and soft power in foreign policy.
• Joseph S. Nye Jr. is dean of Harvard's Kennedy School of Government and author of the new book 'Soft Power: The Means to Success in World Politics.'