My sense of things is this: When Yidden are learning Torah and fulfilling Hashem’s ratzon, we evoke His rachamim and He sends bracha and shalom to the world. For what conceivable reason would He force us to stop learning Torah? There can only be one reason – Hashem, for whatever His purposes are – wants a milchama to occur.
When Yidden learn Torah well, it’s basically impossible for a war to happen. If, however, there must be a war (and it’s not because of our aveiros), then the Yidden need to cease from learning. So what does Hashem do? He selects a rasha nation as a shaliach to inflict a plague (since Hashem will not afflict us directly, as we are not committing unspeakable aveiros) on the world and Torah is forced to cease. When Torah learning ceases, Hashem becomes angry and, in this case, I believe, war will follow.