WASHINGTON -- The 33,000 U.S. troops ordered to Afghanistan two years ago to stop Taliban advances are back home, with military officials claiming that the surge accomplished its objectives.

But did it?

“In mid-2009 there was a real risk that the mission in Afghanistan might very well fail,” Defense Secretary Leon Panetta said recently. “Today the situation is very much different and improved.”

Violence is down, Panetta said, echoing a refrain heard around the Pentagon.

But for all the American blood and treasure invested in the war, some experts who’ve studied it contend that the problem with the military’s claims of success is that the numbers don’t add up. Using them alone, the Taliban is overmatched, and attacks since the surge are down. Yet, they have become more brazen.

“When I was in the Pentagon, I used to see reams of metrics for Iraq and Afghanistan,” said Thomas Mahnken, a former deputy assistant defense secretary for policy planning under Presidents Barack Obama and George W. Bush. “Few had any real meaning.”

Now in its second decade, the war played a supporting role for many years while most of the military and political attention was focused on Iraq. And while the presidential campaign has occasionally veered to foreign policy concerns, like Libya and Syria, Afghanistan as an issue has been missing in action.

Obama and Republican challenger Mitt Romney largely agree on the strategy, which is to remove most American troops by the end 2014.

But after 11 years, Afghanistan remains a battlefield of mixed accomplishments and unforeseen milestones.

Last month marked the death of the 2,000th American service member in the war. It also saw a group of uniformed Afghan soldiers – our supposed allies – turned their weapons on American troops at an Afghan Army checkpoint. It was not the first time. So-called “green-on-blue” attacks have been increasing over the past year.

The end of the surge leaves the American military and NATO with a combined force of about 100,000, supplemented by an Afghan force of 350,000, according to NATO.

NATO and the Pentagon estimate that the Taliban has about 20,000 men. By any definition, the 20-to-1 odds would seem to pose an overwhelming advantage.

But a recent spate of highly organized attacks against allied forces, such as the raid last month in which 15 Taliban got inside Camp Bastion , a major air base in southern Afghanistan’s Helmand province, and killed two U.S. Marines and destroyed six fighter jets, indicate that troop numbers don’t tell the whole story.

Nor do the enemy body counts.

Coming up with numbers to reflect military progress has never been easy, said Mahnken, who teaches national security at the U.S. Naval War College. Even as basic a measure as the number of enemy killed has little meaning against an insurgency, he said.

In fact, military officials refuse to even track exact numbers of enemy killed or captured in Afghanistan. Instead, daily reports from the International Security Assistance Force, the NATO-led coalition, use vague descriptions like “few” or “several,” “multiple” or “numerous;” even “many.”

The measurements can mean anywhere from three to “more than 20.”

Using that math, U.S. and allied forces during the first half of September captured or killed about 400 insurgents. But if the entire Taliban force consists of about 20,000 fighters, shouldn’t losing hundreds every few weeks be a sign of a looming collapse?