Here are the two core paragraphs from the President's speech, outlining the strategy (emphasis added):
"Now let me explain the main elements of this effort: The Iraqi government will appoint a military commander and two deputy commanders for their capital. The Iraqi government will deploy Iraqi Army and National Police brigades across Baghdad's nine districts. When these forces are fully deployed, there will be 18 Iraqi Army and National Police brigades committed to this effort, along with local police. These Iraqi forces will operate from local police stations -- conducting patrols and setting up checkpoints, and going door-to-door to gain the trust of Baghdad residents.
This is a strong commitment. But for it to succeed, our commanders say the Iraqis will need our help. So America will change our strategy to help the Iraqis carry out their campaign to put down sectarian violence and bring security to the people of Baghdad. This will require increasing American force levels. So I've committed more than 20,000 additional American troops to Iraq. The vast majority of them -- five brigades -- will be deployed to Baghdad. These troops will work alongside Iraqi units and be embedded in their formations. Our troops will have a well-defined mission: to help Iraqis clear and secure neighborhoods, to help them protect the local population, and to help ensure that the Iraqi forces left behind are capable of providing the security that Baghdad needs."
What matters here is not the size of forces (though the strategy will not work without a certain minimum force size), but rather their tasks. The key element of the plan, as outlined in the President's speech, is to concentrate security forces within Baghdad, to secure the local people where they live. Troops will operate in small, local groups closely partnered with Iraqi military and police units, with each unit permanently assigned to an area and working its "beat".
This is different from early strategies which were enemy-centric (focusing on killing insurgents), or more recent approaches that relied on training and supporting Iraqi forces and expected them to secure the population.
The new strategy reflects counterinsurgency best practice as demonstrated over dozens of campaigns in the last several decades: enemy-centric approaches that focus on the enemy, assuming that killing insurgents is the key task, rarely succeed. Population-centric approaches, that center on protecting local people and gaining their support, succeed more often.
The extra forces are needed because a residential, population-centric strategy demands enough troops per city block to provide real and immediate security. It demands the ability to "flood" areas, and so deter enemy interference with the population. This is less like conventional warfare, and more like a cop patrolling a beat to prevent violent crime.
This does not mean there will be less fighting -- indeed, there will probably be more in the short-term, as security forces get in at the grass-roots level and compete for influence with insurgents, sectarian militias and terrorist gangs. But the aim is different: in the new strategy what matters is providing security and order for the population, rather than directly targeting the enemy -- though this strategy will effectively marginalize them.
Why the focus on Baghdad? Because about 50% of the war in Iraq happens inside Baghdad city limits. Improving security in the capital therefore makes a major difference. (Not that the enemy will meekly roll over and accept this -- hence the need for more troops and a reserve to deal with the inevitable enemy response, which will probably see spikes of activity outside Baghdad even as security in the city improves.)
There are no guarantees in war, and there is no guarantee that the new strategy will work, or that success will happen overnight if it does work. Iraq is an extremely complex and difficult problem, as all of us know -- if there was a "silver bullet" solution we would have found it by now. All that the new strategy can do is give us a fighting chance of success, and it certainly does give us that.
All of this represents a true departure from previous strategy, but the "surge" is not the strategy -- the switch to population security and a residential, high-force-density, long-term approach is what matters here.