nine weeks and counting
From the BBC:

The new American administrator in Iraq, Paul Bremer, has abolished the ministries and institutions that formed the backbone of Saddam Hussein's power structure.

The Iraqi army - including Saddam Hussein's once formidable Republican Guard - has been disbanded, and will be replaced by a new defence force.

The defence and information ministries, the military and security courts and the Olympic Committee have all been dissolved.

Okay, this is largely a symbolic act, but why wait 9 weeks to do something so basic? It can't be because the occupation is busy with real actions like restoring basic services because they've moved at snail's pace on those as well.

Phil Carter's excellent analysis in the Washington Monthly gives the real answer:

Even the failures of these previous missions demonstrate that manpower is less important to the achievement of military victory than to coping with victory's aftermath. In Kosovo, according to retired Gen. Montgomery Meigs, then commander of the Balkan stabilization force, we were forced to "do less" because the Pentagon claimed it could not send more peacekeeping troops. As a result, says Meigs, "we were unable to run operations inside Kosovo to interdict the internal movement of arms and Albanian-Kosovar fighters to [neighboring] Macedonia." Those armed separatists set off a civil war in Macedonia--stopped only by the timely deployment of more Western troops, including Americans, into that country.

Something very similar happened in Afghanistan. Our biggest failure there occurred in the mop-up stage, following the flight of the Taliban government. Because we had so few troops on the ground, we failed to cut off and destroy the remnants of al Qaeda--including, most likely, Osama bin Laden himself--as they fled into the lawless mountain regions of the Afghan and Pakistani frontier. Our subsequent efforts at nation-building on the cheap have yielded similar results. Our unwillingness to put many troops on the ground has made a mockery of the president's promise for a "Marshall Plan" for Afghanistan. The Western-oriented, U.S.-installed president, Hamid Karzai, controls little more than Kabul, and the rest of the country has already drifted back into warlordism.

Keeping the coalition numbers down may have been a simple miscalculation. The Pentagon's civilian leadership may believe that machinery is everything and boots on the ground are futile. Of course, there's also a fair chance that it was thought a lot easier to sell a fast, clean war with few troops than a long and difficult occupation with hundreds of thousands of troops.

afterthought
The Guardian reports similar problems:

Tony Blair has been told in stark terms that American forces have exacerbated tensions because they have refused to mingle among the local population in the same way as British forces in Iraq's second city of Basra.

The finger of blame is being pointed at troops from the 3rd Infantry Division, the main US forces in Baghdad, who are said to be desperate to return home after bearing the brunt of the military campaign.

One source said: "In the capital the US forces have not adopted the mingling profile with the populace that has been a success in other cities. That is not the instinct of a heavily armoured division that has gone through a tough war."

The failure to secure Baghdad, which contrasts with successes by US and British forces in other parts of Iraq, will have grave consequences for reconstruction. It is understood that US corporations, such as Bechtel and the USAid government department, are reluctant to start repairing Iraq's infrastructure until Baghdad is safer.