The Battle of Yavin
Last revised: 2000.07.27
Objective: Destroy Yavin IV before the Rebels can evacuate.
30 X-wing starfighters.
The Yavin IV moon base defenses.
One Death Star.
You should already know that in what may be the most legendary battle in sci-fi, David slew Goliath.
To be more specific, a lone X-wing fighter succeeded in firing a torpedo down a 2 metre wide exhaust port, destroying the Death Star's main reactor.
Governor Tarkin foolishly ignored the advice of a subordinate and refused to take the attack seriously. Not only did he fail to evacuate, but he also failed to deploy his TIE fighters. Only the ships under Vader's direct command were launched.
One common question is: "why didn't the Rebels evacuate, the way they did at Hoth?" I think the answer is that they were well established in that base, and they didn't have enough time. Some have suggested that a couple of hours should have been enough time, but that is frankly silly. Go ask a factory manager how long it would take to dismantle and package all of his equipment in preparation to move to another building, and then ask yourself how long it would take to dismantle and evacuate an entire military base. The Hoth base was makeshift, and undoubtedly in a state of constant preparation for an evacuation, but the Yavin base was built before the Emperor dissolved the Imperial Senate and unveiled the Death Star. When they set it up, they probably assumed their shield would buy them days to load transports in the event that they were attacked.
Could the Federation have succeeded where the Empire failed?
First, we must define their assets. Obviously, they would have no Death Star. However, we can assume that they would field a fleet as large as any fleet they've ever fielded onscreen. For example, the 600 ship fleet in "Sacrifice of Angels".
Since a fleet like that doesn't present a single target or an Achilles Heel for a starfighter attack, the battle would probably occur around Yavin IV itself. This means that the base defenses on Yavin IV, never seen or described in detail, would come into play. They would have been useless against the enormous weaponry of the Death Star, but against comparatively insignificant Federation starships, it would be a different story. However, it's difficult to imagine their effect since we know so little about them.
In the canon ANH novelization we are informed that "Admiral Motti and his tacticians had expected the rebels' resistance to be centered around a massive defense of the moon itself. They were completely unprepared for an offensive response consisting of dozens of tiny snub ships." This indicates that he expected Yavin IV to have very strong defenses. Given Motti's intelligence data as well as the size and maturity of the base on Yavin IV (compared to the makeshift base on Hoth), it seems reasonable to conclude that Yavin IV probably had defenses well in excess of those on Hoth. These defenses would most likely include a much larger shield, as well as numerous ground batteries hidden in the jungle. It is also possible that they had some capships at their disposal, although they would have wisely sent them away rather than waste them against the Death Star.
We've seen how strong SW planetary shields are; Alderaan's planetary shield demonstrated the astounding ability to resist the Death Star superlaser for more than a tenth of a second. Such shields could easily withstand long-term bombardment from a few hundred Federation vessels, and if such a shield existed on Yavin IV, an attack would have been futile.
Unfortunately, there is no concrete information on Yavin IV's defenses. This gaping hole in our knowledge makes it virtually impossible to predict how the battle would go. It might be anything from a Federation massacre (if Yavin IV has strong defenses and a planetary shield) to a Rebel massacre (if Yavin IV has no defenses). It seems reasonable to me to imagine that the Yavin IV base must have been much more strongly defended than the relatively makeshift Echo Base seen in TESB, but there is no way to verify this one way or another.
It has been suggested that since the Federation is assumed to have intel data, they would know about the planetary shield and they would send the Defiant (cloaked, of course) to sneak inside the shield while it's down, and then destroy the shield generator. However, this tactic assumes that they keep the shield down most of the time, and raise it only when they detect incoming attackers. This wasn't the case in ROTJ, where the shield stayed up all the time, and it certainly wouldn't be the case at Yavin (where they would have turned it on the moment Leia arrived and said she was being followed). Remember that the assumptions about intel data cut both ways: the Feds know about the shield, and the Rebels know about the Defiant's cloaking device. Therefore, the end result is unchanged: it all depends on whether Yavin IV has a planetary shield.
The situation seems unresolvable, but there's one thing we haven't taken into account yet: speed. In the original battle, the Death Star was at Alderaan and had to follow the Falcon to Yavin in order to attack the Rebel base. It was able to make this trip in a matter of hours, thanks to the speed of its hyperdrive system. But this trip, from a core system to the outer rim, would require several decades for warp-driven Federation starships. By the time they arrived, the base would be deserted and Han and Leia's kids would be middle-aged.
Flip side: how would the Federation fare in place of the Rebellion?
First, we must define their assets. Instead of thirty X-wing fighters, they would have thirty runabouts or Peregrine fighters. Their base defenses would presumably consist of orbital defense platforms, although they would be insignificant compared to a Death Star.
If they have capships at their disposal, they wouldn't fare any better than the defense platforms. Much like the Gungan theatre shield in TPM, the ANH Death Star shield was apparently semi-permeable, permitting passage only for slow-moving, small objects (this explains why the X-wings would accelerate to intercept the Death Star, decelerate to match speeds with it, and then "accelerate to attack speed" after passing slowly through the shield). Capital ships would never slip through its shield, thus making them useless (except as clay pidgeons for the Death Star's surface guns).
Therefore, it would fall to the fighters to stop the Death Star, just as it did in the original battle. The fighters would have to lob a torpedo into the exhaust port in spite of the massive jamming which was described in the canon ANH novelization. This means they would have to get close enough to get a target lock and hope that their missiles fly true in spite of the jamming. It also means that they would have to make the trench run just like the X-wing fighters did, for the same reason (to fly in under the impenetrable defensive cross-fire over the port).
This means they would have to fly largely on manual control, while evading TIE fighters and defensive blasts until they can get close enough to launch their missiles. Therein lies the first serious problem: Federation pilots are rarely capable of doing anything on manual control. Riker is considered an exceptional pilot (the best on the Enterprise, as we found out in "Chain of Command"), largely because he can do it while others can't.
A second serious problem involves simple geometry. While an X-wing's proton torpedoes measure less than 0.5 metres in any dimension, a Federation photon torpedo measures 2.1 metres in length and 0.76 metres in width. This means that it is virtually impossible for a photon torpedo to approach the port from the side, make a hard 90 degree turn and enter the port without touching the walls, by virtue of its size. However, micro-torpedoes are smaller, so this problem would only apply to ships which have been outfitted with full-size torpedoes.
A third serious problem involves maneuverability. While we witnessed Luke's torpedo execute a hard turn in ANH requiring many tens of thousands of g's of acceleration, we've never witnessed such maneuverability from a photon torpedo. Photorp turning circles are in the range of hundreds of metres or even several kilometres, not one or two metres. They've never demonstrated the ability to execute anything remotely like the ANH maneuver, which was a 90 degree turn inside a turning circle of one metre.
If the Federation replaced the Rebellion they would be forced to adopt the Rebellion's tactics, which were the only way to attack the Death Star due to its shields, defensive weapons and jammers. But they aren't capable of duplicating Luke's shot into the exhaust port, due to problems with pilot skill and torpedo maneuverability.
Conclusions: The Federation would have no hope whatsoever of even engaging the Rebellion in the Battle of Yavin. As the Rebellion, their torpedoes would have been too clumsy to negotiate the turn into the exhaust port, so they wouldn't have been able to take advantage of the Death Star's Achilles heel. A direct frontal capship assault on the Death Star would, of course, be suicide. I would give the Federation 0 for 2 in this battle.
Jonathan Boyd, for mentioning micro-torpedoes and for his idea about the Defiant cloaking and attempting to sneak under the shield when it's down.