Recently, some have been discussing "backchaining" as a strategic planning technique. In brief, this technique involves selecting a target outcome, then chaining backwards from there to determine what actions you should take; in other words, rather than starting with your current position and extrapolating forward, you start with the desired position and extrapolate back. (As far as I can tell there is very little, if any, difference between this and backward induction in game theory, but I've heard several in the community call this "backchaining" recently and so use that term here.)
For instance, you might say "Okay, to get people on board with this project we'll need to give a presentation. To make a presentation we'll need a slide deck. To make a slide deck we'll need to get the relevant metrics. Therefore, let's go get the relevant metrics."
Backchaining can be useful in that it allows you to ensure that your actions are cutting through to the objective. However, there are some scenarios where backchaining isn't really an appropriate technique - namely ones where the objective is long-term in nature or involves too many unknown unknowns.
One example that might prove fruitful to investigate is that of chess. In chess, backchaining from desired positions can be useful. However, humans simply can't establish long enough chains for this to be a practical tool in long-term planning. It would be absurd to say "All right, this game I'm going to go for a king-and-rook mate on the 'a' file against my opponent's king alone. To do that, I'll need to use the principle of zugzwang to force my opponent's king to move into an unsafe position. To do that, I'll need to..."
Instead, one usually focuses on accumulating generalized advantage in the opening and midgame, and once sufficient advantage has been established one can then transition into planning for specific endgame positions. This approach is much more effective - fixating on too particular a scenario constrains your options, so instead you just focus on building an advantage.
A similar thing is true in other domains. While backchaining can be a useful technique for accomplishing projects with relatively concrete and legible goals, it starts to falter and even become counterproductive when aimed at a target that's too far in the future. It's easy for this type of reasoning to lead to overcommitting to specific paths that may or may not be the best ones to take - better to instead focus on building generalized advantage, at least insofar as you have a reasonable sense of where you're going.
I don't think it's just a matter of long vs. short term that makes or breaks backwards chaining--it's more a matter of the backwards branching factor.
For chess, this is enormous--you can't disjunctively consider every possible mate, nor can you break them into useful categories to reason about. And for each possible mate, there are too many immediate predecessors to them to get useful informaton. You can try to break the mates into categories and reason about those, but the details are so important here that you're unlikely to get any insights more useful than "removing the opponent's pieces while keeping mine is a good idea".
Fighting a war is a bit better--since you mention Imperial Japan in another comment, let's sketch their thought process. (I might garble some details, but I think it'll work for our purposes) Their end goal was roughly that western powers not break up the Japanese Empire. Ways this might happen: a) Western powers are diplomatically convinced not to intervene. b) Japan uses some sort of deterrent threat to convince Western powers not to intervene. c) Japan's land forces can fight off any attempted attack on their empire. d) Japan controls the seas, so foreign powers can't deliver strong attacks. This is a short enough list that you can consider them one by one, and close enough to exhaustive to make the exercise have some value. Choosing the latter pretty much means abandoning a clean backward chain, which you should be willing to do, but the backwards chain has already done a lot for you! And it's possible that with the US's various advantages, a decisive battle was the only way to get even a decent chance at a war win, in which case the paths do victory do converge there and Japan was right to backwards chain from that, even if it didn't work out in the end.
As for defense budgets, you might consider that we're backwards chaining on the question "How to make the world better on a grand scale?" You might get a few options: a) Reduce poverty, b) cure diseases, c) prevent wars, d) mitigate existential risk. Probably not exhaustive, but again, this short list contains enough of the solution space to make the exercise worthwhile. Looking into c), you might group wars into categories and decide that "US-initiated invasions" is a large category that could be solved all at once, much more easily than, say, "religious civil wars". And from there, you could very well end up thinking about the defense budget.