Author’s Note: I wrote this a long time ago for a role-playing forum where a friend and I were arguing over why the Star Wars ships were fighting at ranges that would to be comparable to knife-fights, when their ranges for fighting were actually much greater. I couldn’t fully answer him for that reason beyond simple “it wouldn’t fit into a movie screen if they did that” at the time; that is until I researched a bit and made my own conclusions. The theory I developed is below.Evolution and Doctrine of the Imperial Star Destroyer
As we all know Star Destroyers are iconic vessels of the Star Wars universe. Star Destroyers are depicted as large dagger-shaped and extremely well-armed warships, serving in large numbers in the immense Imperial Starfleet (estimates have put the number at 25,000 total over the entire galaxy) and elsewhere, including in the service of the Galactic Republic, the New Republic, the Galactic Federation of Free Alliances — and possibly even in the corporate war fleets of the Confederacy of Independent Systems.
The designation "Star Destroyer" refers to the common dagger-hulled combat vessels used by the Empire in the three films of the original trilogy. They are commonly referred to as Imperial-class Star Destroyers, their official designation as of a short time after the declaration of the newly formed Empire. During the earliest weeks of Imperial regime and the latter days of the Clone Wars, the class was known as the Imperator-class. This is regarded as the most common class of Star Destroyer, and one of the most important symbols of the Galactic Empire, serving the Imperial fleet for at least five decades. When the term "Star Destroyer" is used without further qualification, it usually refers to ships of this class.
So where did these massive ships come from and how did they come about?
To discover this we must go back to the origins of the Clone Wars, just after the initial battle of Geonosis. At this time the Republic was given a clone army from a supposed Jedi benefactor. This was later found to be a devious plot of Palpatine’s. The ‘Grand Army of the Republic’ as it was dubbed, was an army of clones made to be to be the perfect fighting soldiers; and as such were outfitted with the best possible equipment and fighting vehicles.
To serve as transports and fighting vessel was the Acclamator-class Assault Ship. The 752-meter-long Acclamator class assault ship was the first capital ship designed for use with the Grand Army of the Republic, referred sometimes simply as the "Republic assault ship." It can be considered the ‘grandfather’ of Star Destroyers, for it was the Acclamator that set the precedent, or design, of the arrow-shaped hull. However, unlike its later cousins it was not designed as a space combat starship or even a cruiser; rather, it was designed as a heavily armored and armed troop transport for planetary bombardments and surface landings.
However the Republic was lacking in space combat worthy vessels. To settle this the newly outfitted for war Republican shipyards and such major manufacturers as the Kuat Drive Yards and the Rendili Stardrive began building newer models of ships to settle into the role of a space combat ship.
Both KDY and RS were racing against each other to create a ship that would be bought by the Republic, each wanting the major contracts and cash that would come along with it. The RS were at somewhat of a set-back, as the Acclamator was made by the KYD and as such had only very basic schematics to work with, however they were undaunted and designed what was named the Victory-class Star Destroyer.
The Victory Star Destroyer was designed to be a jack-of-all-trades ship: capable of taking on and defeating enemy capital ships, fielding a fairly large fighter compliment, and being able to carry a large compliment of clonetroopers. It was bought in large numbers by the Republic. At 900 meters long the Victory became the largest capital ship capable of entering the atmosphere, this was exemplified when a certain Captain Tarkin (before reaching higher rank) used his Victory Star Destroyer to crush a large crowd of protestors at what became known as the Ghorman Massacre. It should be noted that the Victory II, a later model of the Victory, was not capable of entering atmosphere.
Against the Victory design the KDY created another arrow shaped vessel after their successful Acclamator. Designed to be a starfighter carrier/destroyer the Venator-class Star Destroyer was the Kuat Drive Yards master piece of the time. Beating the Victory in length at 1,137 meters, the Venator was the largest Star Destroyer yet then made. The Republic bought roughly equal numbers of these vessels as they had Victory Destroyers.
Now, at the time of the Clone Wars, the most basic naval tactic was to fight your enemy en masse with hopefully superior numbers and often times in traditional firing lines (similar to how the British often would have their Redcoat soldiers line up neatly and fire into the enemy repeatedly) by which the two enemies would engage each other and, thanks to the dimensions of space, become fluid lines of battle.
Clone War commanders based their tactics on using their ships (Venators, Victorys, Acclamators) as a base of firepower, or a weapons platform. This was meant to establish a powerful rear or base. Fighters then took up the spearhead of an attack and were on missions to destroy not only enemy fighters but also to inflict damage upon enemy ships, or 'weapons platforms'. This tactic was little changed from the beginning of the Clone Wars to its end, and the tradition and tactic as such was carried into the Imperial Fleet when Emperor Palpatine took power.
Now we have ourselves a clear understanding of the past, and the three vessels that pre-dated the Imperial Star Destroyer and were its ancestors.
Everyone has to understand that the Star Destroyer MkI and MkII were based upon this evolution. That evolution of the Venator and Victory class Star Destroyers. A weapon is designed according to the need of the battlefield. Its parameters based upon battlefield experience. When Imperial Commanders were fighting at Endor, they were doing so with a paradigm mindset and tactical needs according to the doctrine of heavy weapons platforms backed with fighter compliments. (Which ultimately they did not do, seeing as the Emperor forbade them to engage, only to hold.)
This in turn reflects upon the battles of the Clone Wars. The Clone Wars were in a sense similar to the battles upon the seas between the 1500s-1940s. You lined up your capital ships, tried getting a better position by maneuver, and then wailed at your enemy until he was dead or retreated. Thus Venators provided a powerful addition to the Grand Army by having eight heavy turbolaser cannon batteries, proving to be an extremely useful weapons platform (some captains even opened their fighter bays and let their Clone vehicles fire out with their weapons, adding to their firepower). (The Victory had quad turbolaser batteries but no heavy batteries as the Venator did.)
The Imperial Fighting Doctrine was based upon Old Republic Grand Army Doctrine. Many of the officers from the Old Republic were transferred into the Imperial Fleet (the Emperor could hardly afford to kill off all the most brilliant and best fleet officers now that the Independent Star Systems were defeated leaving him no other pool of effective fleet commanders). Thus we are provided with Old Republic paradigm within the new Imperial navy.
In addition to this old paradigm of capital ships being heavy weapons platforms combined with effective fighter squadrons became the Emperor's ideal of 'Rule by Fear'. Imperial fleet engineers decided to take the already proven and effective design of the Venator and the Victory (based upon results from the Clone Wars) and combine it with that ideal of Rule by Fear. From that was born the Imperial Star Destroyer.
Not only did it dwarf the Victory and Venator classes, but it provided a far heavier weapons base, larger fighter compliment, heavier shielding and hull, and provided the Imperial Fleet with the final addition to their doctrine. The Star Destroyer, or Imperator, was the epitome of Imperial Strategic and Psychological Doctrine: Rule by Fear and Fight by Maximum Power (provided by the largest capital ship then in existence, i.e. the ISD).
A better way perhaps to understand the development of the ISD is to study the development of Nazi Germany's Panzers: from the Panzer I to the Panzer VI, known as the Tiger. Their development of tanks was based upon what they encountered on the field of battle. The same happened for the Empire.
The innovative tactics of using heavier armed and more maneuverable fighters as well as a newer class of starship (Mon Cal) allowed the Rebel Alliance and then the New Republic to challenge and thus utterly wipe out several decades worth of Imperial Doctrine. Admiral Ackbar took his cruisers into closer range of ISDs, not only making them less likely to be targeted by the DSII but also because ISDs perform at their best only when at a distance and as a weapons platform. Thus Ackbar's more flexible strategy (albeit more forced by Calrissian) both confused Imperial ship commanders and provided them with an unprecedented situation; for their experience and doctrine gained from the Clone Wars did not provide them with any viable alternative.
Knowing now about the doctrine to use it, we need to look at the ISD as a weapon.
So the ISD is not weak because of its design. No weapon is 'stupid'. It is simply that those who built it and used it were not prepared for the type of situations which examples like the Battle of Endor presented.
Therefore it is understood that the reasons for the way in which the Galactic Empire conducted its fleets was a result of more than 25-30 years of experience based on older practices and doctrines: the dominating role of the capitol ship as a weapons platform, the large amount and presence of star fighters, and the lack of innovation that those two precedents leave for a commander. (well, an average commander. We all know several Imperial commanders that used ISDs in ways that were both innovative and incredible.)And now pretty pictures to take your mind off my horrible theory. Shiny.