Put aside for a moment whether you think an adulterous affair should have ended the near mythical career of Gen. David Petraeus. A much larger question seeks an answer: Was he as unwise in war as he was in love?

For what becomes of the Petraeus military legacy has profound implications for both the way America wages war and for its future willingness to intervene with force abroad.

That's why in the past couple years, far removed from any hints of scandal, there has been growing concern in military and diplomatic circles about the general's signature command concept that made him the most revered U.S. commander in a generation — the so-called Petraeus doctrine.

Spelled out in a landmark 2006 U.S. Army and Marine combat manual, the Petraeus doctrine was once heralded as a revolution that turned U.S. thinking about the Iraq and Afghanistan wars on its head.

When it came out, a frustrated U.S. was bogged down in Iraq in a hopeless attempt to fight insurgents with heavily armoured conventional forces.

This was an offshoot of the so-called Powell doctrine from the 1990s Gulf War  (named after retired general, later secretary of state Colin Powell), which insisted that, to avoid a Vietnam-like quagmire, American force should only be used when it was both overwhelming and quickly decisive.

But then Petraeus, a Princeton- (PhD) and West Point-educated airborne commander came along and argued that, given the new circumstances, things had to change.

Toss of the COIN

For Petraeus, this all-or-nothing Powell doctrine approach had to be swept aside by full adoption of highly flexible counterinsurgency warfare, which became known as COIN.

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Gen. David Petraeus in the spring of 2011, just before taking over at the CIA. Is his legacy justified? (Akira Suemori / Associated Press)

As Petraeus rose to command all forces in Iraq in 2007 his doctrine called for soldiers to leave their ubiquitous armoured vehicles to patrol "among the people," even if it meant taking more casualties initially.

The new objective was for American soldiers to win the hearts and minds of the inhabitants by respecting local customs, providing security for schools and hospitals and the like, and even godfathering ceasefires among factions.

This Petraeus doctrine proved a media and political sensation, and even became a publishing bestseller.

The timing was perfect and politically astute. For liberals, Petraeus seemed to promise less brutal fighting and fewer civilian casualties; while to Bush-era neo-conservatives it promised an ultimate warrior to fix their own botched wars from total meltdown.

Petraeus's stock rose even higher as he successfully lobbied Washington for a substantial troop "surge" to boost public security, first in Iraq, and later in Afghanistan in 2010, which seemed in both cases to reduce the levels of violence, at least initially.

A relentless self-promoter, Petraeus would go on to take full advantage of Washington's gushing media and political class — both acutely aware that 12 generals from George Washington to Eisenhower ultimately became president.

Would Petraeus heed the call one day? (There was speculation for the longest time that Barack Obama made him CIA chief in April 2011 because the president didn't want Petraeus running for the Republicans in the recent election.)

The former Bush White House especially seemed awed by a general ablaze with medals (Petraeus wore 54 combined U.S. and foreign decorations or badges) and was also a media darling who clearly felt himself smarter than your average politician.

As former general Paul Eaton memorably described it in 2007, in Petraeus "you have a guy with a bright, subtle intellect who is capable of playing chess in a complicated world, and we have an administration that is struggling with checkers."

Examine the legacy

In the U.S. military, though, not everyone was uncritical.

Many in higher ranks saw him as an opportunistic pitchman for the Bush war aims, and a "Teflon general" quick to disown his own setbacks.

Petraeus' former superior when he was in Iraq, Adm. William Fallon, the then head of Central Command is reported to have once denounced Petraeus as a sycophant.

But most accounts have portrayed Petraeus as an extremely intelligent, flexible, fiercely hard-working commander who had the rare charisma to inspire a whole generation of junior officers to embrace his thinking.

Which raises the question: Did his counterinsurgency master strategy actually work?

Or was it just another false promise of success that future commanders should be wary of?

In hindsight, the Petraeus tactics seemed to work only partially in Iraq in a limited period, and not at all well in Afghanistan.

Yes, the insurgency lessened in Iraq on the heels of the Petraeus doctrine and following the U.S. troop surge, which gave Obama his opportunity for an exit.

Most analysts, however, say that situation was due less to counterinsurgency tactics than to internal Iraqi politics: al-Qaeda's excesses turned civilians against them, while Iraq's large Shia population cut ruthless political deals that gave them the power they hold today.

In Afghanistan, there were no such political conditions and so counterinsurgency has largely failed.

As both U.S. and allied troops, including Canadian, found out the hard way, putting lightly armed troops out among the locals proved far too costly in casualties to sustain.

Western governments simply aren't prepared to endure the kind of long, expensive, grubby, and usually frustrating campaigns that counterinsurgency requires, and which, even more to the point, local populations simply loathed because they still felt occupied by strange, sometimes rude, foreigners.

In some ways, it is surprising that it took Petraeus and his followers so long to figure this out.

In truth, much of the Petraeus doctrine began to fade long before he doffed his star-studded uniform for the top CIA post.

In his final months commanding in Afghanistan, Petraeus seemed to embrace many of the once-criticized tactics of the old guard, including frequent bombing and drone attacks that inevitably killed not only Taliban, but civilians as well, forfeiting any goodwill that COIN might have brought.

As George Friedman, the founder of the global intelligence company Stratfor recently wrote, counterinsurgency tactics inevitably failed in Vietnam, Iraq and Afghanistan because occupied locals could not be won over by force.

The U.S. must find a better way to operate in the future, he warned, for "the record for these wars does not instil optimism."

This is why it could be a great misfortune if Petraeus is now to end up as a historical figure brought down simply by risky sex.

It's far more important that Americans — and the rest of us — examine and learn from what look to be deep flaws in the military experiment that bears his name.