Today marks the end of the Gates era. As I write, Defense Secretary Robert Gates’s farewell ceremony is underway. At almost the same time, Gen. David Petraeus, incoming CIA director, should have his nomination approved.

These two men have defined America’s defense policy and martial qualities for much of the last decade and they have done much to maintain the faith of the American people in their military at a time when that faith was sorely tested.

We thank both of them for the enormous sacrifices they have made on our behalf. We worry about the great challenges their successors face and wish them well.

Below, I’m including a story that broke yesterday and should provide food for thought for Leon Panetta and Gen. Dempsey as they begin their struggles to maintain America’s influence in the world.

Washington: A group of Brown University researchers released a report today estimating the costs of America’s current wars in blood and treasure, an effort sure to draw enormous quantities of skepticism, anguish, fear and loathing.

The basics: the report estimates the wars in Afghanistan, Iraq have already cost $3.2 trillion and could end up costing as much as $4.4 trillion. That stands in stark contrast to President Obama’s recent estimate that the wars have cost $1 trillion. Also, the Cost of War report says the wars will consume 225,000 lives and create 7.8 million refugees by the time they end.

“At least 137,000 civilians have died and more will die in Afghanistan, Iraq, and Pakistan as a result of the fighting at the hands of all parties to the conflict,” according to the report.

Military experts are likely to be highly skeptical given the report’s estimates of notoriously difficult to track civilian casualties in very difficult to penetrate societies. For example, the report says as many civilians may have died in Pakistan as have died in Afghanistan — 12,000 to 14,000 people– but they admit they don’t know with any reliability. “The armed conflict in Pakistan, which the U.S. helps the Pakistani military fight by funding, equipping and training them, has taken as many lives as the conflict in neighboring Afghanistan,” it says.

Now, an impartial observer might separate the deaths in Pakistan from those in Afghanistan and Iraq. After all, deaths at the hands of the Pakistani Taliban and other groups operating in Pakistan, along with the Pakistani military and security forces, should not just be lumped in with the other conflicts because the U.S. helps the Pakistani military. Pakistan’s civilian deaths are, for the most part, the result of the country’s lousy domestic politics and are not (Obama, his friends and the Haqqani network folks excepted) the result directly or indirectly of US operations.

And there are assertions like these: “The wars have been accompanied by erosions in civil liberties at home and human rights violations abroad.” OK, few rational people would disagree that the U.S. has done some pretty rotten and illegal things since 911, but this is so broad as to raise the hackles. This would seem to say that Iraq and Afghanistan, at least, now have governments that are less free and that inflict more human rights violations than those that existed when the U.S. stumbled in. That just seems, in the legal tradition, counterfactual unless you believe the Taliban and Sadaam Hussein ran flawed but fundamentally decent governments.

A great deal of the costs the Brown University academics cite are not yet incurred because they will arise from the future costs of treating veterans — $589 billion to $934 billion if you project out to 2051. That, dear readers, is a lot of projecting.

The report does the American people the service of again focusing our attention on these issues. A less ambitious effort might have served us all better in the long run.