There’s a doctrine in warfare known as proportional response. If one country seizes or destroys a ship of another country, the second country should respond on the same level, or perhaps escalate the response slightly. The second country shouldn’t do something “horrific,” like bombard or destroy an entire city. Except… sometimes that works, and then everyone speculates on why it shouldn’t have been done… even when such an act may have actually cost fewer lives than a continuing conflict.
In a limited logical fashion, proportional response makes sense, because a rapid escalation is hard on the people on one side for certain, and possibly for both sides, but that depends on the conflict and the cultures and demographics of the countries involved. Escalating proportional responses effectively lost the Vietnam War for the U.S. Given cultures and demographics, the U.S. had only two possible effective choices, although these choices are far clearer in hindsight than they were at the time. One was to realize that South Vietnam was a lost cause and make some sort of agreement with the north. The second would have been an immediate and total scorched earth attack on North Vietnam, which was deemed politically infeasible and could have escalated into a world-level conflict. By the time Nixon even thought of using overpowering aerial warfare, the war was effectively lost, even though the U.S. “won” almost all pitched battles, including the Tet Offensive.
One other lesson that comes out of studying warfare is that the military is almost always “fighting the last war,” particularly in times of social and technological change. There’s a reason for this. Tactics are developed based on available weapons and logistics, and upon past experience. When one side finds a way to use something new or apply something existing in a new fashion, there’s a time lag before the other side figures it out. And sometimes that time lag can be fatal.
In fantasy, of course, as authors we can war-game such doctrines, but one thing I’ve done that’s bothered some readers is that I’ve followed history with regard to innovation. What I mean by that is that when one side uses magic or technology in a new way, it takes the other side time to adjust… and they may never make the adjustment if they don’t have decent communications. First, they may not have heard about the innovations or tactics. Second, they may not believe what they’ve been told, or they may believe that they are different/better than previous commanders. Even though General Billy Mitchell showed that airpower could sink battleships in 1923, many U.S. admirals still didn’t really believe it would happen in a “real war,” until Pearl Harbor. And third, they may not have the time or training to change, even if they’re willing to change. The French army couldn’t adjust to the German blitzkrieg in time to keep France from falling.
I’ve also noticed, and maybe it’s just the books I’ve read, that “wars” in fantasy either tend to be heavy on blood, guts, grit, and action with all of the impact on the combatants…or treat war almost superficially. If history is any indication, war has impacts on all levels of society on both sides, even for the greatest of empires, and any empire that is devoting a significant percentage of its resources to continual warfare isn’t going to endure that long. Peace and prosperity prolong nations and empires, provided, of course, that the empire has a strong enough and talented enough military force to squelch small brushfire insurgencies or border incursions before they become a real threat.