It depends on your viewpoint
If you lean towards Deontology, then yes it is fine as the assumed ends would justify the means. By more strict ethical breakdown, one could argue that the loss of any lives was the incorrect policy to go by, but then you get into the argument of what else could have happened blah blah blah. I feel that it was not truly justified because of that fact. This was not a two-way street there and several other possible options existed: engaging the gov't of Japan more comprehensively, enlisting the aid of other countries, etc. Granted, all of the other options are completely theoretical as far as solvency, but so were the two initial options. In my eyes, we had a million different options, and they were somehow boiled down to two gruesome ideas.