Last time I looked, a "rational strategy to kill the enemy" need not be moral. Also, the last time I looked, there were degrees to what was moral and immoral, and some strategies to kill the enemy were relatively more moral (or relatively less immoral) than other strategies to kill the enemy. For instance, a strategy that involves actually targeting civilians is barbaric and relatively less moral than a strategy that does not actually target civilians.
One of the more telling things about the worldwide debate over the morality and ethics involved in the Israeli/Palestinian Conflict is how often these days people say that Hamas is morally superior to the Israeli government simply because Hamas has killed only one or two civilians while Israel has killed hundreds. To believe that, you must believe that intention counts for nothing in questions of morality. Hamas intends to kill civilians. It targets its rockets at civilians. Israel, so far as I can see, seldom intends to kill civilians, and if and when it does, the decision to kill civilians seems to be made a low level, rather than at a high level of the government. I loathe the Israeli government, and would take a happy and glorious **** in every one of their faces, if I could, but intellectual honesty does not permit me to believe the government has a policy of targeting civilians.
If the Israeli government were purposely targeting civilians, a lot more civilians would be dead than are dead.