I noted today, via tweet from President Trump, that “..when I asked, how many will die. 150 people, sir, was the answer from a General.”
Now, we have done a few casualty estimates for conflicts: 1) The 1991 Gulf War estimate done by Trevor Dupuy that was briefed to the House Armed Services committee in 1990 and was the source of his book If War Comes, 2)  the Bosnia casualty estimate that The Dupuy Institute did for the Joint Chiefs of Staff (JSC) in 1995. This is discussed in depth in Appendix II of America’s Modern Wars, and 3) The Iraq casualty estimate that we did in 2004 for Center of Army Analysis (CAA) and OSD Net Assessment. This is discussed in depth in the first Chapter of America’s Modern Wars. So, we know something about casualty estimation and actually have a documented, provable track record.
We have no idea what casualty estimation was done for a strike or conflict with Iran. We have not been involved in that. Most likely, if a properly developed casualty estimation was done, it was done with a range of results. For example, our Bosnia estimate was that in the case of an extended deployment (which is what was done) it was estimated that there was a 50% chance that U.S. killed from all causes in Bosnia in the first year would be below 17 (12 combat deaths and 5 non-combat fatalities) and a 90% chance U.S. killed would be below 25 (see page 308 in America’s Modern Wars).
So, I am guessing that President Trump was not told that there would be 150 killed, he was probably given a range of estimates, of which that was probably the upper boundary of that range. Still, these numbers get people’s attention. I gave a briefing one morning on our Iraq estimate after a three-day weekend…and as one colonel commented during the briefing “This is a hell of a briefing to wake up to after a long weekend.” (see page 18, America’s Modern Wars).
