our Army due to Iraq update

The 15-month terms were always seen as a temporary measure. Talk to soldiers, and they will tell you that 15 months of continuous combat duty is simply too wearing.

Enlistment rates are down; junior officers are dropping out at rates unseen since Vietnam days. The war in Iraq is the main reason for both trends. The Army is already stretched to the bone. Senior officers and Gatess are deeply worried that maintaining this breakneck pace for much longer might break the all-volunteer Army.

If the terms of duty are cut back to 12 months of deployment, followed by 12 months home, it is not clear whether even 15 brigades can be sustained in Iraq for very long. And once troop levels fall below 15 brigades, it is not clear—as they approach 10 brigades, it is very unlikely—that the mission of securing the Iraqi population (the essence of counterinsurgency) can be sustained.

The clock is also ticking on the other games that are keeping ultraviolence at bay. After the Sunni-U.S. alliances defeat the jihadists, or reduce their ranks to a manageable level, nobody expects the Sunni fighters—who, before their "awakening," spent much of their time shooting and blowing up American soldiers—to become pliant citizens. Also, ethnic cleansing has Balkanised some neighborhoods and destroyed the mix of Sunnis and Shias.

In sum, U.S. forces may soon have more eruptions to damp down—or, to switch metaphors, more holes in the Iraqi dike to plug up. And the task will be more daunting still once the troop-levels decline.

All this is why Gen. Petraeus and most other officers refrain from wild cheering at the reports of declining casualties and violence. T