As the boy says: "War is neither glamorous nor fun. There are no winners, only losers. There are no good wars, with the following exceptions: the American Revolution, World War II, and the Star Wars Trilogy."
This is interesting, first, because Mark Kleiman's reader seems to take it for granted it's easy enough to find high quality pro-war matter pre-1700. Yet there were no good wars in that period! Something to think about. (Yes, yes, 'a long time ago, in a galaxy far, far away'. Still. Looks futuristic to me.) So I think Mark should start by looking at the extensive selection of Star Wars novels Amazon lists. It is not true MLA members are ashamed to be seen reading such stuff. I myself have only read one. Greg Bear's. It wasn't very good. (Not that I'm an MLA member either.) In general it is much easier to launch a fundamental assault on the notion of 'literary merit' than it is to defend a lot of senseless slaughter. Defining literary excellency up rather than defining martial deviancy down, if you will. The main ingredient of a rigorous assault is a pun in the title. For example: "I Sing of Arms And De Man." Then you write about how Star Wars novels illustrate themes discussed in Blindness and Insight. (How Vader fails to appreciate that by striking down Obi Wan, etc.. And the boy is dangerous, etc.)
More seriously? Watership Down? From Here To Eternity?
There is an ambiguity in the category 'pro-war'. War is seldom presented as straightforwardly and uncomplicatedly, inherently desirable - like love or friendship or happiness. Conan: "To drive your enemies before you and hear the lamentations of their women." That view is the exception, not the rule, and is generally not expressed at novelistic or epic poetic length.
War is often presented as terrible but necessary. The terrible unavoidability of it may be a means to the end of glory. Possibly this just boils down to, "to have a perfectly sound excuse, since they started it, to drive your ememies before you and hear the lamentations of their women." But it can also mean: war is an occasion for exhibiting virtues like physical courage, loyalty, self-sacrifice. War can be terrible and unnecessary, yet glorious. That is, an occasion for those not to blame to show their quality. War can be a learning experience, and can be presented as such. You might learn that 'war is hell'. A valuable lesson. But books about characters learning such lessons are not pro-war, plausibly. In general, as we move out along this line of possibilities, war becomes more and more equivalent to accident, hardship, obstacle, disaster, conflict. These are the engines that turn the wheels of character and action, i.e. the novel. But mostly novels aren't explicitly pro-accident, pro-hardship, etc. But this just gets us to the Nietzschean question: is the honest thing to say that we really are pro-all these things, because we demand that the wheels turn? (He who wills the wheels to turn must will the engine?) Ergo, almost all - perhaps all - good anti-war novels count as pro-war novels. Because whoever writes and reads such stuff is Conan, with a touch of pacifist on top. Part of you loves war, part of you hates it. So both parts get to sit back and enjoy a good anti-war novel, chock full of warry goodness.
Heaving ourselves up out of the existential abyss of our guilty Conan-ness, perhaps 'pro-war' should be defined, for literary purposes, as: expressive of the view that, without war, certain moral goods would be rendered unavailable; goods which are essential to the good life, or basic ingredients in it, or particularly tasty.
Conversely, the following would not be sufficient to qualify a work as 'pro-war': war is terrible but not perfectly preventable and sometimes conduces to moral goods. This is not sufficient because the same thing could be true of a novel about the aftermath of a bus accident, e.g. The Sweet Hereafter. I take it that novel is not classifiable as pro-bus accident.
But this just casts us back down into the Nietzschean abyss. Life without conflict would not be worth living. Being pro-conflict in general means being pro-war now and again. Here is a test case: Is Brave New World a pro-war novel, because Mustafa Mond's methods of preventing war, among other things, are morally abhorrent? It's not a war novel, obviously. But it's not clear why a pro-war novel should need to be a war novel You can have a pro-peace novel with no peace, hmmm yes?