In interviews in recent weeks, Gen. David Petraeus has been taking a line on what will happen in mid-2011 that challenges President Barack Obama’s intention to begin a troop withdrawal from Afghanistan by that date. This new Petraeus line is the culmination of a brazen bait-and-switch maneuver on the war by the most powerful military commander in modern U.S. history.

It represents a new stage in the process by which Petraeus, abetted by his allies in the Pentagon, Secretary of Defense Robert Gates and Chairman of the Joint Chiefs of Staff Mike Mullen, has appropriated much of the power over decisions on war policy that rightly belongs to the commander in chief.

President Obama agreed to the troop surge for Afghanistan last November on the explicit condition that Petraeus and the Pentagon agreed to begin handing over real responsibility for security to the Afghan army and begin a real drawdown of U.S. troops by July 2011. The account by Newsweek columnist Jonathan Alter, based on interviews with those who participated in the meetings on Afghanistan last fall, shows that Obama was quite clear and determined about the war policy he wanted in Afghanistan:

“There would be no nationwide counterinsurgency strategy; the Pentagon was to present a ‘targeted’ plan for protecting population centers, training Afghan security forces, and beginning a real – not a token – withdrawal within 18 months of the escalation.”

Alter reports precisely what happened in the climactic meeting of Nov. 29, 2009:

“Inside the Oval Office, Obama asked Petraeus, ‘David, tell me now, I want you to be honest with me. You can do this in 18 months?’

“’Sir, I’m confident we can train and hand over to the ANA [Afghan National Army] in that time frame,’ Petraeus replied.

“’Good. No problem,’ the president said. ‘If you can’t do the things you say you can in 18 months, then no one is going to suggest that we stay, right?’

“’Yes, sir, in agreement,’ Petraeus said.”

Petraeus was agreeing that, if the counterinsurgency strategy was not going well at the end of the 18 months, he would not use that as an argument that he needed more time to demonstrate the success of the strategy. Obama was using a JFK-like tactic to “box in” Petraeus.

But Petraeus has now revealed in the media offensive that began in mid-August that his agreement to the Obama plan was the “bait” in his bait-and-switch maneuver.

He has now let it be known that he may not go along with beginning a troop drawdown in July 2011 as he had agreed with Obama. When asked on Meet the Press on Aug. 15 whether he might tell Obama that the drawdown should be delayed beyond mid-2011, Petraeus said, “Certainly, yes.”

And in an another challenge to the agreement with Obama, Petraeus suggested in an interview with ABC News last week that there could no clear-cut “handoff” of primary responsibility for security to the ANA next July. Instead, Petraeus described the July 2011 “transition” in Afghanistan as “You do a bit less and the Afghans do a little bit more instead of saying, ‘Tag, you’re it. You take the ball and run with it. We’re out of here.’”

Setting aside his obviously tendentious characterization of a real security handoff, Petraeus’s baby steps approach to the post-July 2011 transition is clearly at odds with Petraeus’s assurance to Obama last November that he could “train and hand over to the ANA” by July 2011.

These new Petraeus line on July 2011 represents the “switch” in his bait-and-switch maneuver. Along with Gates and Mullen, Petraeus had agreed to one set of terms for the troop surge last November. Now he is advocating an altogether different war policy.

Given the widely publicized excerpt from Alter’s book in Newsweek last May, Petraeus’s commitment to Obama last November is hardly a state secret. But in American politics, if the news media decide not to refer to an event, it is equivalent to expunging it from effective historical memory.

That is exactly what has happened to the Obama-Petraeus agreement. Not a single reference to that agreement has appeared in news media coverage of Petraeus’s statements relating to July 2011.

Instead of firing Petraeus for his perfidy on the November 2009 agreement, meanwhile, Obama has thus far passively accepted Petraeus’s bait-and-switch maneuver, just as he truckled to Petraeus and Odierno on withdrawal from Iraq last year.

The Petraeus bait and switch is a yet another fire-bell in the night – a warning that Petraeus has gained unprecedented power over U.S. war policy. By drawing Obama into a deepening of U.S. military involvement in an unnecessary and self-destructive war on the false pretense that he supported Obama’s policy and then turning on that November 2009 policy once he became commander, Petraeus is acting as though he intends to prevent the president from carrying out the policy on which he had decided.

Unless Petraeus’s bait and switch is decisively rebuffed by the White House, the country’s descent into de facto military control over war policy will continue and accelerate.