The sudden departure of General David Petraeus from the CIA probably tells us more about the state of our nation than it does about Petraeus. President Barack Obama should not have accepted his resignation.

We now seem to care more about the sex lives of our leaders than the real lives of our soldiers. We had years of failed generalship in Iraq, for example, yet left those commanders in place. Petraeus’s departure again demonstrates we are strict about intimate behavior, but extraordinarily lax about professional incompetence.

“A private who loses a rifle suffers far greater consequences than a general who loses a war,” Lieutenant Colonel Paul Yingling wrote in the Armed Forces Journal in 2007.

Americans severely judge some forms of private behavior between consenting adults, if one party is a public official. Yet we often resist weighing the professional competence of such officials ‑ even when they clearly are not doing a good job.

This is not, as some say, because we are a puritanical nation. Rather, our standards have changed in recent decades ‑ and not for the better.

Consider, we don’t know precisely the relationship between General Dwight D. Eisenhower and his driver, Kay Summersby, during World War II. But it is evident that it was romantic in some ways, and, by her later account, quite intimate. If Ike were judged by today’s standard, he would have been sent home in disgrace from Europe, and the war likely would have been worse without his calm, determined and unifying presence. He was not fired. But dozens of other Army officers, including 16 division commanders in combat, were relieved of command during the war ‑ for professional reasons.

Matthew Ridgway was another great American general, serving in World War II and Korea. Over a few months in 1951, in one of the best but lesser-known episodes of American generalship, Ridgway turned around our fortunes in the Korean War. Like Ike, Ridgway was fond of female companionship. He almost seemed to get a new wife for every war. In his personal papers on file at the U.S. Army archives in Carlisle, Pennsylvania, interspersed with discussions of how to improve combat leadership in the Korean War, there are some terse notes from his first wife’s lawyer.

This change may have occurred in part because we as a nation no longer have much military experience and no longer prize military effectiveness, nor even are capable of judging it. In past wars, soldiers eager to survive would forgive their leaders a multitude of lapses if they believed those leaders knew their business.

We also may have changed because so few of us have “skin in the game,” to use a phrase one often hears from the parents of soldiers. Certainly, if I had a loved one in a combat zone, I would care much more about the military skills of the people in charge than I would about their sexual lives.

Another reason we may also hesitate to judge professional competence is that it is difficult in small, messy, unpopular wars to know just what victory looks like. Yet ironically, in Iraq, Petraeus was one of the few clear successes we had among our top leaders ‑ first in commanding the 101st Airborne Division Mosul in 2003-04, and then as the overseer of “the surge” that began extricating the United States from Iraq in 2007.

Our diminished standards speak to a lack of seriousness in the way we wage our wars. No, the conflicts in Afghanistan and Iraq are not existential, as World War II was. But a soldier blown up in Afghanistan this year is every bit as dead as one machine-gunned on Omaha Beach 68 years ago. Today’s soldiers deserve to have the most competent leaders we can provide, just as the men of D-Day did.

Some of my friends in the military argue that a general who cannot keep his marriage vows cannot be trusted to keep his word. But we all fail in different ways throughout life. As Petraeus’s revelations last week reminded us, he is human. We have asked much of him, sending him on three tours of duty in Iraq and one in Afghanistan. Yet when the time came for us to be generous in return, we were not.

I have known Petraeus for about 15 years, and his supposed lover, Paula Broadwell, for a portion of that time. I am not close to either. I do not approve of what they reportedly did. But I also don’t think it is any of my business.

By contrast, taking care of our soldiers should be a concern of all of us. Where are our priorities?

PHOTO: General David Petraeus at a dedication ceremony at Camp Victory in Baghdad, January 31, 2008. REUTERS/Ceerwan Aziz