Stretch them to the breaking point and then increase the pressure. Collapse will follow. In the early days of the siege of Richmond, Lee admitted that if Grant had been able to bring one or two more brigades to bear he would have been crushed as he had no reserves left.
It appears that this is what Bush has done in Iraq according to the Weekly Standard. It appears that Bush made one of the most audacious moves in civilian control of the Military since Lincoln appointed Relentless Grant to lead the Union Armies.

In September, Rumsfeld had rejected the idea of a surge when retired general Jack Keane, a former vice chief of staff of the Army and a member of the advisory Defense Policy Review Board, met with him and Pace. Keane insisted the “train and leave” strategy, as Bush referred to it, was failing. He proposed a counterinsurgency strategy, the addition of five to eight Army brigades, and a primary focus on taking back Baghdad. Rumsfeld was unconvinced. But now, with Bush favoring a strategy nearly identical to Keane’s, he didn’t object. “Rumsfeld was never a lose guy,” a Bush adviser said. “He always wanted to win.”
With Bush’s connivance, Cheney asked the chiefs a series of questions designed to ease their qualms about a surge. What would be the consequences of losing in Iraq? Was the Iraqi army capable of quelling the sectarian violence without substantial help from American troops?
The chiefs had real grievances to air, and they didn’t hold back. Schoomaker cited the stress on combat forces from repeated tours of duty in Iraq and Afghanistan. That, Bush told me, was “the main thing I remember from that meeting. That was clearly a factor in some of the people around the table’s thinking .??.??. if you sustain our level, much less increase the level, you could, Mr. President, strain the force, which is an important consideration.”
Bush agreed that strain was a problem. Then he delivered a sharp rejoinder, touching on a theme he returned to in nearly every meeting on Iraq. “The biggest strain on the force would be a defeat in Iraq,” he said. Winning trumped strain. To alleviate the strain, the president committed to enlarging the Army by two divisions and increasing the size of the Marine Corps. The chiefs had two more complaints. The military, practically alone, was carrying the load in Iraq. Where were the civilians from the State Department and other agencies? Again, Bush agreed with their point. He promised to assign more civilians to Iraq. (The number of provincial reconstruction teams was soon doubled.)
Their final problem was the unreliability of Iraq’s Shia government and army. Would Iraqi forces show up and do their part in the surge? And would they act in a non-sectarian manner, treating Sunnis the same as Shia? Bush said he’d get a public commitment on both counts from Maliki before making a final decision on the surge. And he did.

The article goes into General Petraeus’ call for more brigades. The initial plan called for a one or two brigade surge. Petraeus asked for 5 brigades and got them.
On top of that Congress voted to increase the size of the military. The Democrat controlled Congress. Obviously it is never wise to come up short of divisions in wartime. It could adversely affect re-election prospects. Even of Democrats.
H/T Instapundit
Cross Posted at Power and Control