AMERICAN commanders in Baghdad have been here before. In 2004, a
year after the invasion that toppled Saddam Hussein, they handed
the reins of security to freshly trained forces of a once-again
sovereign Iraq and encouraged them to take control of the main
towns. But the Iraqis proved unable or unwilling to hold the
line against the insurgents. The Americans delayed their exit
and set about retraining the Iraqis. This time will it be
different?  Probably yes. Since they again took control of the
urban areas early last month, Iraqi security forces, now
numbering 274,000-plus regulars and interior-ministry troops
along with 277,000 police, have surprised American commanders
with their new assertiveness. If anything, the Americans now
find their former understudies too aggressive. “They're like
kids with a brand-new muscle car, out there burning rubber,”
says an American officer. “It almost scares you.”  That may
sound condescending. But there is genuine cause for worry.
Overconfidence among soldiers can be as d