Washington: The balance between the Army’s resources and its commitments is “precarious” even as the number of soldiers deployed to Iraq and Afghanistan declines, because the total size of the Army is going down at the same time.

If the demand for troops continues to drop as planned, Army leaders say they should be able to handle the nation’s military missions. Any deviation from the plan, however, voids that guarantee. That’s the message clearly written between the lines as the service positions itself to fight the coming budget battles.

“‘Precarious’ is a good word,” a senior Army officer told Breaking Defense. “The reason the margin of error is so thin is that it’s all about people.”

On the demand side, top soldiers warn, any unforeseen crisis in Afghanistan or elsewhere around the world would strain the service. On the supply side, the danger is that the Army manpower might be cut faster or further than the current plans allow — cuts which no less a figure than Chief of Staff Ray Odierno has repeatedly warned are likely. “Do I think we’ll go below 520 [thousand soldiers]? Probably,” Odierno said Monday morning. “Do I know what that number is going to look like? I do not.”

Odierno spoke to reporters at the Association of the US Army conference in Washington, D.C. That afternoon, during a panel discussion at the conference, top Army officials wrestled with how the uneasy balance between downsizing and drawdown would affect the Army’s training and deployment cycle, infamously known ARFORGEN (“Army Force Generation”). The panelists spent most of their time on the better world to come after the current wars, when the military would finally have manpower to spare for long-neglected missions like building partnerships with foreign militaries around the world. But they also struck some nervous notes about how the Army can get from here to there.

“The end strength of the Army as of the end of August was 569,000,” said Karl Schneider, principal deputy assistant secretary of the Army for manpower and reserve affairs, “but we had over 700,000 soldiers on active duty.”

That’s the level the Army has maintained for years now, with mobilized Army Reserve and National Guard troops making up the difference. And Reserve Component troops will remain critical to meeting demand in the future, which means they’ll remain on call for years to come. Indeed, the need to further “operationalize” the Reserve Component and bring its soldiers more smoothly into the ARFORGEN cycle of training and deployment was emphasized by both RC panelists, Army Reserve Command chief Lt. Gen. Jack Stultz and Army National Guard deputy director Maj. Gen. Timothy Kadavy. That means the “weekend warriors” will be spending months deployed abroad on a regular basis for the indefinite future.

For its part, the active Army is giving up the temporary increase of 22,000 soldiers authorized by Sec. Robert Gates. When that reduction is completed sometime in fiscal year 2013 — which, it’s worth noting, is at least a year before the tentative December 2014 date for withdrawal from Afghanistan — “then we’ll take our permanent force structure, in the active component, down to 520 [thousand],” said Maj. Gen. Peter Bayer, director of strategy, plans, and policy for the Army staff’s operations directorate, known as G-3/-5/-7. (That’s the same 520,000 target that Odierno predicts the Army will go below). But even as the supply of soldiers shrinks, Bayer went on, “demand stays very much the same between now and ’14. There’s a slight downward trend” — but only slight.

So is the Army shrinking too fast, faster than the demands of Afghanistan go down? Not officially. “Based on known projected demand, the decline in resources, and the directed reduction in AC [active component] endstrength to 520, we think it’s in the band of moderate and acceptable risk,” Bayer said when pressed. “However… we’re not very good at predicting” the future, he went on, pointing to the morning’s news of sectarian riots in Egypt.

Or, as Donald Rumsfeld might have said, “known” projected demand is well and good, but there are both known unknowns — the demands we can guess might arise but which we can’t project accurately — and unknown unknowns — the demands we can’t even guess. In short, said Bayer, “it is beyond complicated.”