Is there a time for war? I would argue that the list of 14 antitheses in chapter three of Qohelet are not presented as things that are all good or proper. In fact, the list alternates between what is desirable (birth, healing, peace, etc.) and undesirable (death, killing, war, etc.). But the point of the entire list is to show the hebel הֲבֵל or absurdity of human existence “under heaven.” All of these things happen outside of human control and because everything is determined, there is no profit in human toil. Verse 11 is the key to the interpretation of this passage. The first phrase emphasizes the fact that God determines the time for everything, אֶת־הַכֹּל עָשָׂ֖ה יָפֶה בְעִתּוֹ “He brings everything to pass precisely at his time” (Note that I took referent of the possessive pronoun on “time” as God). The rest of the verse highlights the absurdity of human existence: while there is a time for everything, only God knows the timing: God has “put הָעֹלָם in their hearts, yet they cannot find out what God has done from the beginning to the end.” The times are set and there is nothing that we can do about it. This unpleasant conclusion is that God has played a trick on all of us. He has implanted in us an awareness that of our inability to know. Our only compensation is that we can enjoy the good time — though note that even here it is a gift controlled by God. I don’t think that this list can be used to justify any human actions, whether the decision to enter into a war or to go dancing.
I object to ever describing war as “just, right, and/or good.” Sadly, war is a much too frequent reality in this radically fallen world, but that doesn’t mean it is ever good. War is a manifestation of evil and no matter what noble reasons one may have for waging war, the evil of war will pervade all who participate. A prime example of this would be World War II. If any war could be deemed a “justifiable” war, I would think it would be the one. That being said, the war in the Asia-Pacific theatre ended up with the U.S. dropping atomic bombs on civilian targets — which I would find difficult to ever consider “just, right, and good.” Thus, while war is a reality and perhaps even necessary for a nation to engage in once all other options have been exhausted, it is never a “good” option. If this is “quibbling” forgive me; I believe it is an important distinction.