At
http://www.whiterosesociety.org/ there is a graph of number of American soldiers killed in Iraq vs time.
Looking at it, I noticed something that somewhat surprised me. The rate of deaths is remarkably constant: since May or June 2004, soldiers have been dying at a rate of about 70 every month with relatively little variation month-on-month.
However, between March 03 an May 04 the death rate was an - again, moderately steady - 40 or so per month. Then, around April or May, there is a sudden spate of killings, and then it settles back down to the steady but higher rate.
Can anyone explain this in terms of change in the situation in Iraq around that time? Was it the American forces moving into the Southern Shi'ite cities?