The changes of the world's structure in the 20th century were mainly brought about by war. In this century, two world-scale wars, namely, World War I and II, and the Cold War, broke out.
The world has not been clearly reconfigured since the end of the Cold War, which signalled the collapse of a two-polar structure in the world. For some time after the Cold War ended, the United States itself was not entirely sure of where its main threats came from, whether from the still destructible nuclear stockpile left over by the Soviet Union, or China's rapid development, or somewhere else.
For a certain period after the end of the Cold War, the United States focused its main energies on developing new kinds of weapons and building a missile defence shield to overpower its potential strategic rivals. In 1999, the world's sole superpower waged the Kosovo War to consolidate its dominance in Europe and squeeze its strategic scope towards Russia. In 2000, George W. Bush claimed China was a strategic competitor of the United States in one of his presidential campaign speeches.
All the blustering was a clear signal of the US' uncertainty over who was its main foe.
The September 11 terrorist attacks in New York and Washington in 2001, however, greatly shocked the United States. Even in the Pearl Harbour Incident of December 7, 1941, mainland US was free from direct attacks from Japan although its Pacific Fleet suffered heavy losses.
The September 11 event shows that the biggest threat to the US homeland is neither sophisticatedly-armed big powers, nor its alleged strategic adversaries, but irregularly-based terrorist organizations.
Facing such unprecedented challenges, the US Bush administration substantially adjusted its global strategy, aimed at not dealing with threats from strategic rivals, but from terrorism and the proliferation of weapons of mass destruction.
In the wake of September 11, the "Bush Doctrine" came out, in which the United States created "axes of evil" and "pre-emptive" strategies. It linked counter-terrorism and the prevention of proliferation to the reformation of so-called "rogue states" and "failed states."
Under this doctrine, the United States launched two military actions in Afghanistan and Iraq within two years. It reviewed the structure of the US military forces, and drafted programmes for redeployment of US forces overseas.
Under this doctrine, the United States has tightened its control of the Middle East, Central Asia, Southeast Asia and Northeast Asia, strengthened its response ability to this outstretched "unstable arc," and put forward its "Big Middle East" reform programme.
It all testifies that Washington's anti-terror campaign has already gone beyond the scope of self-defence.
And these latest moves, when seen with the background of the Gulf War and the Kosovo War, have made it obvious that the United States has not changed its Cold War mentality and that the country is still accustomed to applying military means to deal with various threats, visible or invisible.
The philosophy of the "Bush Doctrine" is in essence force. It advocates the United States should rule over the whole world with overwhelming force, military force in particular.
Hardly strange, then, that Bush and his administration still insist on arguing that their decision to go to war in Iraq and US policy on the issue were right.
But the world's situation in response to the war is in effect a negative answer.
In Iraq, the United States did win a war in the military dimension, but it is far from winning peace for itself and the Arab country.
On the contrary, Washington has opened a Pandora's box, intensifying various intermingled conflicts, such as ethnic and religious ones.
The US case in Iraq has caused the Muslim world and Arab countries to believe that the superpower already regards them as targets of its ambitious "democratic reformation" programme. This perception has increasingly aggravated the long-brewing conflicts between the United States and the Muslim world.
Now, Washington's predicament in Iraq has become daily news.
On June 28, the White House hurried to transfer Iraq's power to the country's interim government. But the handover was of more nominal than practical significance. Currently, 150,000 US troops are still deep in the Iraq quagmire, and the death toll steadily increases.
The Iraq War has made the United States even more unpopular in the international community than its war in Viet Nam. Bush did not even dare to meet the public on the streets when he visited Britain, the closest ally of the United States.
From US pre-war military preparations to postwar reconstruction of the country, the rift between the United States and its traditional European allies has never been so wide.
It is now time to give up the illusion that Europeans and Americans are living in the same world, as some Europeans would like to believe.
The Iraq issue has also presented a heated topic for the US presidential election.
Over the past year, some American think-tanks and politicians have had soul-searching reflections on the issue and given their criticisms.
Many of them believe that the Bush administration did not objectively and clearly assess challenges and difficulties facing the United States when it applied the pre-emptive strategy. In so doing, the administration was only practising the same catastrophic strategy applied by former empires in history.
Both history and practices of "the myth of empires" have demonstrated that the pre-emptive strategy will bring the Bush administration an outcome that it is most unwilling to see, that is, absolute insecurity of the "American Empire" and its demise because of expansion it cannot cope with.
Just as Joseph S. Nye said, the paradox of the US force theory is that the world's politics have already changed, and even for the world's most powerful country, it is impossible to realize its key goals merely through its own strength, just like that by the ancient Roman Empire.
Neo-unilateralism has seriously underestimated the role a country's soft power and international systems can play, thus denting important means that Washington can apply to practise its new national security strategy.
The Iraq war was an optional war, not a necessary one, and the pre-emptive principle should be removed from the dictionary of the US national security, former US Secretary of State Madeleine Albright also said.
The Iraq War has also destroyed the hard-won global anti-terror coalition.
Mounting hostile sentiments among the Muslim world towards the United States following the war have already helped the al-Qaida terrorist network recruit more followers and suicide martyrs. Instead of dropping, the number of terrorist activities throughout the world is now on the increase.
The US' call for help from the United Nations (UN) for Iraq's postwar reconstruction work once again shows that in the current world, unilateralism is not appropriate in solving international affairs.
The Iraq War provides another negative example of international relations in the new century.
In an increasingly interdependent world, in which the benefits of every country have been closely intertwined, the damages a war can cause will be far more than the benefits it can bring. Any superpower can impossibly force the international community into accepting its own norms merely through displaying its military muscle.
The current US predicament in Iraq serves as another example that when a country's superiority psychology inflates beyond its real capability, a lot of trouble can be caused.
But the troubles and disasters the United States has met do not stem from threats by others, but from its own cocksureness and arrogance.
The 21st century is not the "American Century." That does not mean that the United States does not want the dream. Rather, it is incapable of realizing the goal.
In this century, all big powers should compete in a peaceful way, instead of military means.