(CNN) -- On the fifth anniversary of the war in Iraq, with nearly 4,000 American lives lost, is Iraq really on a path to peace?
Three factors are often cited in explaining the improvement in security: the U.S. troop surge, the political "awakening" of the Iraqi people, and the cease fire ordered by anti-American cleric Muqtada al-Sadr.
But some say a controversial fourth dynamic is at play as well -- cash, being doled out by the barrelful.
It's a truth many hold to be self-evident that more American troops translate into less Iraqi violence. As President Bush said in January's State of the Union speech, "Some may deny the surge is working, but among the terrorists there is no doubt."
But some military experts do have doubts, arguing there's actually a mightier force at work -- hundreds of millions in cash given to Iraqis, for everything from picking up garbage to taking up arms against al Qaeda. Watch Bush discuss the troop surge »
Retired Army Col. Doug Macgregor, a longtime critic of top Iraq commander Gen. David Petraeus, said it's a "cash-for-peace" scheme that is bound to backfire. Watch CNN's Kyra Phillips interview with Gen. Petraeus »
"Normally when you begin paying off your enemy on the scale that we are, it is seen by your enemy as well as others as a tacit admission of failure, not of success," Macgregor said.
It's hard to pin down exactly how many millions are going to former insurgents to switch sides, but Macgregor argues the result is artificial progress.
"What we've done is we've also flooded the Sunni-Arab insurgents with cash to create a temporary cease-fire to reduce the numbers of U.S. casualties," he said.
Gen. Petraeus' former deputy commander bristles at the suggestion that the U.S. is bribing bad guys to back off.
"That is such a simplified look at it. It's much more complex than that. I believe it to be the right thing to do. It's about reconciling them with the rest of the government of Iraq. It's a confidence-building measure in reconciling them with Iraq," Lt. Gen. Raymond Odierno told CNN.
Former Defense Secretary William Cohen is concerned that direct payment is not "particularly savory," but concedes it may be necessary "to buy the support of people who otherwise would be a raid against you."
"Is that helping to turn the tide? If it's only a question of a tactical distribution of money for a short period of time, then it won't stand up, and it will be reversed the moment we leave," Cohen said.
But U.S. commanders on the front lines insist anger, not greed, is what's behind he so-called "awakening," and has given rise to grass-root groups called *"Concerned Local Citizens" and "Sons of Iraq." Watch Bush's remarks on the fifth anniversary of the war »
"When we first started these programs, these guys weren't getting paid a dime," said Col. John Charlton, 1st Brigade Commander with the 3rd Infantry Division.
"We didn't advertise, you know, 'Join the police force, and we'll give you money.' These guys lined up by the hundreds because they were sick and tired of what al Qaeda was doing to their communities, and they knew that they had to stand up and fight."
So that happens when the money dries up?
Critics, Macgregor among them, predict a quick return to civil war.
"We have to understand that this expedient policy of paying your enemy is very dangerous. It's fragile, and eventually, hatred of the foreign occupier overwhelms greed," he said. E-mail to a friend