WASHINGTON - President Barack Obama presented a case Tuesday for sending 30,000 more U.S. troops to Afghanistan that included both soaring rhetoric and a new emphasis on its necessity for U.S. national security.

Obama said the escalation was for a "vital national interest" and invoked the threat of attacks from the Afghanistan-Pakistan border area, asserting that such attacks "are now being planned as I speak".

Despite Obama's embrace of these new national security arguments, however, he has rejected within the past few weeks the critical link in the national security argument for deploying tens of thousands of additional troops - the allegedly indissoluble link between the Taliban insurgency and al Qaeda.

Proponents of escalation have insisted that the Taliban would inevitably provide new sanctuaries for al Qaeda terrorists inside Afghanistan unless the U.S. counterinsurgency mission was successful.

But during September and October, Obama sought to fend off escalation in Afghanistan in part by suggesting through other White House officials that the interests of the Taliban were no longer coincident with those of al Qaeda.

In fact, intense political maneuvering between Obama and the top U.S. commander in Afghanistan, Gen. Stanley A. McChrystal, over the latter's troop increase request revolved primarily around the issue of whether the defeat of the Taliban was necessary to U.S. anti-al Qaeda strategy.

The first round of the effort was triggered by the leak of McChrystal's "initial assessment", with its warning of "mission failure" if his troop deployment request was rejected. The White House fought back with anonymous comments quoted in the Washington Post Sept. 21 that the military was trying to push Obama into a corner on the troop deployment issue.

One of the anonymous senior officials criticized a statement by Adm. Mike Mullen, chair of the Joint Chiefs of Staff, that the war in Afghanistan would "probably need more forces".

To avoid being outmaneuvered by the military, Obama suggested in a press conference that the legitimacy of the Afghan government might now be so damaged by the blatantly fraudulent Aug. 20 election as to put into question a counterinsurgency strategy such as the one advanced in McChrystal's assessment.

Obama also raised a red flag about the conventional argument from national security, saying he wasn't going to "think that by sending more troops, we're automatically going to make Americans safe".

Within a week, his national security adviser, Gen. James Jones, began to raise that issue explicitly.

In an interview with Bob Woodward of the Washington Post, Jones suggested the question of why al Qaeda would want to move out of its present sanctuary in Pakistan to the uncertainties of Afghanistan would be one that the White House would be raising in response to McChrystal's troop request.

McChrystal's rejoinder came in a speech at the International Institute for Strategic Studies in London Oct. 1, in which he went further than any previous official rationale for the war. "[W]hen the Taliban has success," said McChrystal, "that provides sanctuary from which al Qaeda can operate transnationally."

He was apparently arguing the Taliban wouldn't even have to seize power nationally to provide a sanctuary for al Qaeda.

Only three days later, however, the New York Times reported that "senior administration officials" were saying privately that Obama's national security team was now "arguing that the Taliban in Afghanistan do not pose a direct threat to the United States".

That "shift in thinking", as the Times reported, was an obvious indication that the White House was preparing to pursue a strategy that would not require the additional troops McChrystal was requesting because the Taliban need not be defeated.

One of the senior officials interviewed by Times said the administration was now defining the Taliban as a group that "does not express ambitions of attacking the United States". The Taliban were aligned with al Qaeda "mainly on the tactical front", said the official.

A second theme introduced by the official was that the Taliban could not be eliminated because it was too deeply entrenched in the country – quite a different goal from that of the counterinsurgency war proposed by McChrystal.

That was an expression of resistance to what was soon reported to be a McChrystal request for a "low risk" option of 80,000 troops, combined with a suggestion that 20,000 troops would be the "high risk" option.

But Defense Secretary Robert M. Gates was determined to turn the White House around on the issue of McChrystal's request. He was well aware of Obama's political sensitivity about not being seen as on the wrong side of his national security team, and he effectively used that to force the issue.

Gates worked with McChrystal, Mullen, and Secretary of State Hillary Clinton on a plan that would be presented to the White House as their consensus position on Afghanistan strategy.

The plan, as the New York Times reported Oct. 27, was presented by an administration official as a compromise between the plan put forth by Vice President Joseph Biden for concentrating essentially on al Qaeda, and McChrystal's counterinsurgency plan. It would be ostensibly aimed at protecting about 10 population centers, leaving the rest of the country to be handled by Special Operations Forces with the assistance of drones and air power.

But the catch was that McChrystal was demanding an expansive definition of "population centers", which would include most of the Taliban heartland of the country.

McChrystal was still going to get his counterinsurgency war under the Gates plan.

Notably absent from the Times report was any suggestion that Obama had given even tentative approval to the proposal. Only Obama's advisers were said to be "coalescing around" the proposal. But "administration officials" confidently asserted that the only issue remaining was how many more troops would be required to "guard the vital parts of the country".

That confidence was evidently based on the fact that Obama's national security team had already agreed on the options that would be presented to the president for decision. Two weeks after that report, Obama's press secretary Robert Gibbs said he would consider four different options at a meeting with his national security team Nov. 11.

The four options, as the Times reported the day of the meeting, ranged from a low-end option of 20,000 to roughly 40,000 troops. And Gates, Mullen and Clinton had "coalesced around" the middle option of about 30,000 troops.

Gates and his allies had thus defined the options and stacked the deck in favor of the one they were going to support. And the fact that Obama's national security was lined up in support of that option was already on the public record.

It was a textbook demonstration of how the national security apparatus ensures that its policy preference on issues of military force prevail in the White House.

Although Obama bowed to pressure from his major national security advisers to agree to the 30,000 troops, his conviction that the Taliban is not necessarily a mortal enemy of the United States could influence future White House policy decisions on Afghanistan.

Obama's speech even included the suggestion that the defeat of the Taliban was not necessary to U.S. security. That point could be used by Obama to justify future military or diplomatic moves to extract the United States from the quagmire he appeared to fear only a few weeks ago.