Expect more obfuscation owing to seasonal effects: insurgent activity drops when the temperature pushes 110 degrees.
Economists deal with seasonal fluctuations all the time: inflation, GDP and unemployment are invariably reported on a seasonally adjusted basis.
I decided to do the same for monthly troop fatalities. Here is my graph of the seasonally adjusted data:
I see generally higher fatalities in Apr-Aug 2007, though others may view the graph differently. Data is like that.
It would be no surprise if military fatalities increased during the surge, given that there were more troops on the ground. I’d like to do the same exercise for civilian fatalities, but I understand there’s a break in that series.
Tech details: I used multiplicative Holt Winters seasonal smoothing in Stata. I am frankly not familiar with that particular procedure and there are others. Furthermore, the adjustment process will be noisy as the monthly dataset is only about 4 years long. So I won’t call this conclusive evidence. Some may find it interesting though.
Anyway my point is that there are well understood tools to deal with seasonal effects. Just don’t expect to read about them in the funny pages.