When Vader enters the Hoth System with the Imperial Fleet, he’s holding a winning hand. What follows next is a reminder of two military truths that apply in our own time and in our own galaxy: Don’t place unaccountable religious fanatics in wartime command, and never underestimate a hegemonic power’s ability to miscalculate against an insurgency.
The analysis summarized above, namely that the so-called Empire bungled an opportunity deliver a devastating blow to the so-called Rebellion, makes a critical unwarranted assumption. Namely that it was in Darth Vader’s best interests to 1) destroy a secret base; 2) neutralize a “politically potent symbol,” Princess Leia Organa; and 3) eliminate a “promising proto-Jedi,” in Luke Skywalker.
If you accept that Mr. Vader’s ultimate aim is — as he says later in the same movie, “Empire Strikes Back,” that depicts the so-called debacle on Hoth — to “rule the galaxy as father and son” with Mr. Skywalker, then the outcome of the military action on Hoth becomes largely irrelevant. The military costs of defeat are presumably negligible, if you assume that the so-called Empire is truly galactic in scope, and the political costs may actually further Mr. Vader’s goals. Indeed, as he tells Mr. Skywalker, the whole idea is to “destroy the Emperor.”
In this way, it can be seen that a victory on Hoth, depending on the scale, might have been more devastating to Mr. Vader. He needs a viable Rebellion to justify his use of Imperial resources in the recruitment of Mr. Skywalker. Without the Rebellion, you probably wouldn’t see two Star Destroyers cruising together, let alone the half-dozen Mr. Vader takes to Hoth. And Ms. Organa is a powerful, if frequently inept, symbol of the resistance movement. Likewise, Mr. Vader needs Mr. Skywalker to remain motivated to become a Jedi, and a living, breathing Ms. Organa contributes mightily to that, as a love interest (or a sibling) in need of protection.
The important thing for Mr. Vader is to keep Mr. Skywalker engaged in galactic politics and metaphysical moralizing. A demoralized Mr. Skywalker, perhaps working as a farmhand on Tatooine (drinking heavily and picking fights in Mos Eisley), is of no use to Mr. Vader. The overt, if bungled, show of military force on the ice planet is a demonstration that the cause of the so-called Rebellion is in an urgent phase — but, importantly, not a futile one. There is no doubt that the tumult drives Mr. Skywalker’s decision to continue his so-called Jedi training and develop his ability to manipulate the so-called Force.
It seems like a contradiction, but that decision only accelerates Mr. Vader’s timeline. As was clearly shown in the newest “Star Wars” movies, the Force does not discriminate; good Jedis can move to the Dark Side as easily as Black Friday consumers at the revolving doors of Macy’s. In other words, Mr. Skywalker’s sojourn on Dagobah is like the ramp on a ski jump, with Mr. Vader’s open arms waiting at the bottom of the hill.
It’s a classic bait and switch. Mr. Vader uses a political dispute to mask his desire to rehabilitate his relationship with his son, and possibly his daughter. The end (galactic domination) justifies the means (carnage on Hoth).