*Ahem*
Does that not describe the start of ESB?
Um, no? "Scurrying around," in other words "running around," suggests no acknowledgement of a stationary home, i.e., a base. The Rebels are set back their base, the troops lost defending its evacuation, and heavy equipment that they did not have time to evacuate.
Okay. Based on only what we see in ESB, what did the Empire gain? What was their ‘victory?
Merely finding the Rebels in the opening scene?
Because we don’t see what happens to Cloud City.
They explicitly say they didn’t achieve their goals on Hoth.
And even assuming we count Sidious and Vader’s personal Sith-y goals under ‘Empire’, Luke doesn’t turn.
So...what did they win? Recruiting the neutral Lando for the other side?
It’s posible for the protagonists to lose, without the villains ‘winning.’ The Pyrrhic victory is a pretty normal storytelling device.
You know, besides the Bothans who we find out about in the sequel, a much more important seed to Rebel victory is planted in TESB itself: The possibility of Vader turning against the Emperor is hinted at when Vader suggests to the Emperor that Luke could be turned instead of killed. I'm talking here about the kind of thing that Vader ends up doing in ROTJ, as opposed to the offer he makes to Luke in TESB to team up against the Emperor. In retrospect, based solely on what we're told in TESB but under the assumption that Vader isn't lying about being Luke's father, that's pretty obviously Luke's father pleading for his son's life.
However, as it stands, without confirmation as to who Luke's father is, we only know that somebody's been lying to Luke. But we also know that Vader's lying to somebody, either Luke or the Emperor, or both. It's not simultaneously possible that Vader wants to overthrow the Emperor and rule the galaxy with Luke by his side and that Vader wants to help turn Luke to become an ally of the Emperor. But if the first possibility came to pass, that would still be a victory for the bad guys, even if the Emperor is no longer in the picture.
Luke may have escaped Cloud City, but the possibility of a dark path laid before him and the possibility of his familial connection to the evil he is fighting were not in the bargain when he started out, at least not in any way that he knew, however afraid Uncle Owen might have privately confided that he was to Aunt Beru that Luke had too much of his father in him. That shadow of evil casting itself over Luke is a victory for evil, and a victory for the Empire that is based on evil.
Is it the whole war? No, of course not. But it's a battle won. Vader managed to meet Luke and give him the option to help overthrow the Emperor. In so doing, Vader also managed to sow doubt in Luke about his own cause.
EpIV just represents a battle won. The
Death Star might be destroyed, but Vader escaped, the Emperor still lives, and the Empire is just fine. The war's not settled; do we call that a draw? No. The good guys won that one.
In ROTS, Sidious becomes Emperor, and the Republic becomes the Empire. Yoda, Obi-Wan, Luke, and Leia live, but do we call it a draw? No. The bad guys won that one.
In EpV, the Empire manages to strike back. The Empire's cause is advanced, whereas the Rebels' is curtailed. The stakes are redefined in major ways that seem to favor evil.
P.S. Cloud City is seized by the Empire, the possibility of another Rebel base denied. There really isn't any doubt, since Lando sounds the alarm, and it's not like once there the Empire could be expected to just let it revert to a hands-off state.