As the U.S. marks the 13th anniversary of 9/11 and contemplates renewed military action in Iraq, some observers warn that America is a fading power.

"There was a time when America would whisper 'coup' and nations would quake," says historian and University of Wisconsin professor Alfred McCoy, noting that in a 20-year period up to the mid-1970s, the CIA assisted in dozens of military coups that toppled governments.

Some historians believe the American reaction to the 2001 attacks actually accelerated the decline of the U.S. empire. Look no further than the ongoing quagmire in Iraq, the unachievable goals in Afghanistan and paralysis over Syria.

Military historians who've traced the patterns of empire note that when an empire is in decline, it indulges in feats of "micro-militarism" – small interventions that it cannot win, but still undertakes because imperial pride is at stake.

"We couldn't get rid of Hugo Chavez. Despite our support, the Green Revolution in Iran failed," McCoy offers by way of example.

In his 2004 book The Sorrows of Empire, scholar Chalmers Johnson wrote that embedded in the nature of empire is payback, and that following the attacks on Sept. 11, 2001, radical neoconservatives in the U.S. embraced the idea that "it is America's job to police the world."

This fuelled an orgy of military spending. In 2004, there were 725 known U.S. bases around the world, according to the Pentagon; today, there are over 1,000.

'America is not an empire'

America has often been called the most powerful empire in human history, yet U.S. political elites have often stated the opposite.

Former president George W. Bush once said, "America is not an empire." Donald Rumsfeld, his secretary of defense, stated "we're not imperialistic."

Intense debates have sprung up in recent years about how America has played the grand imperial game.

British citizens embraced notions of empire, but Americans want to be seen to be benevolent rulers. The British believed in having a "civilizing" influence; Americans call it "democratizing."

Chalmers Johnson calls both terms "self-deluding propaganda."

British historian Niall Ferguson believes that America, to its detriment, hasn't been forceful enough in pursuing its imperial quest. "It is an empire in denial so America might end up a colossus with attention deficit disorder," he wrote in his 2004 book Colossus: The Rise and Fall of the American Empire.

In a 2004 interview on CBC Radio's Ideas program, libertarian thinker Doug Bandow echoed this sentiment, saying, "this broad agenda of empire is completely dead if Iraq keeps going the way it's going. In fact, if Iraq dies, I think the American empire is gone."

A cost of trillions of dollars

Economist Joseph Stiglitz estimates military interventions in Iraq have cost America over $1 trillion in direct costs, and two trillion in future costs.

When asked what has been accomplished — besides a lot of death and destruction — Alfred McCoy says, "Not a whole lot."

All of which invites the question, How do you assess when an empire is dead?

The cost of foreign wars, a deteriorating middle class and a poorly performing educational system are only a few of the many variables that have added to America's woes.

That's why a new genre of academics, who call themselves "declinists," has emerged in recent years.

These scholars are charting the weakening of the American empire. McCoy is one of them, and believes the reign of the American empire will be over by 2025.

Even more telling, perhaps, is that the National Intelligence Council, the supreme analytic body within the American intelligence community, has also been reading the tea leaves. It says the days of the American empire, militarily, will be over by 2030.

Tune into CBC Radio's Ideas program on Sept. 11 at 9:05 p.m. (9:35 pm in Newfoundland) to hear the full documentary, or click "The Sorrows of Empire" link at the top-left of this page.