Flak gun

The idea of point defense goes back to before most species even had the ability to orbit their planets, much less the formation of a galaxy spanning civilization. The idea was always to destroy or deflect incoming fire before it could damage you or your position. While energy weapons required shields to do this, the idea was still soundly applied against proton torpedoes, concussion missiles, starfighters, and mass driven rounds.

With advanced automation, computers, and faster-than-light sensors, detecting and destroying projectiles enroute would be easy. Unfortunately, as technology advanced, so did the ability to beat that technology, and the heavy ECM environment of combat rendered all that moot. Incoming shots could manuever and hide themselves to evade targeted CIWS fire. The result was a return to an even older concept, that of the flak gun. Shells would be fired in the general area of the target, which would then explode, filling the area with shrapnel. Though effective planetside, it was in space combat that it really shined - with no atmosphere to slow the shrapnel and the far higher velocities used the shrapnel became incredibly deadly.

Flak guns were a tertiary defense employed by most warships, including the Death Star, Imperator class star destroyer, and  Providence class star destroyer. It also appears to have been carried by some AT-AT models.

Behind the Scenes
The presence of flakbursts has been present and debated since 1977, when the A New Hope novel described "explosive solids" being used against the fighters. For a time, it was believed that turbolasers themselves had the ability to flak burst, based off descriptions of flak being used against the Millennium Falcon and rebel snowspeeders in The Empire Strikes Back, but the advent of DVDs allowed tech-minded fans to point out that a number of flak bursts were actually shield interactions. The debate was finally settled with the release of the final film, which showed once and for all that there was a separate weapons system of mass drivers used to provide the antifighter flak described in the novel. However, the flak bursts could also be the end of the life of a laser bolt. According to the Law of Conservation of Energy, the energy contained in a bolt could not simply dissapear, but be released, most likely in the form of a small explosion.

Appearances

 * Star Wars Episode III: Revenge of the Sith
 * Star Wars Episode IV: A New Hope
 * Star Wars Episode V: The Empire Strikes Back