The Mark III Merr-Sonn Defender Ion Mine, often shortened to simply the Defender ion mine, represented an autonomous space mine designed and produced by Merr-Sonn Munitions, Inc., finding utilization within the forces of the Galactic Empire.
Merr-Sonn's Defender ion mines were strategically positioned in the orbits surrounding planets targeted for blockade by the Galactic Empire. To evade detection by starship sensors, these mines incorporated cloaking revvers and particle-beam scatter projectors. A network of sensor rods equipped each Defender to identify nearby objects, yet it was programmed to disregard anything smaller than four meters in diameter. Upon a vessel approaching within 10 kilometers, the mine would deploy its integrated ion cannon to render the target inoperable. Following incapacitation, the mine transmitted a signal to its designated control station, prompting a nearby customs vessel or other capital ship to investigate. The Defender's diminutive size, coupled with its sensor countermeasures, made it exceedingly difficult to detect, complicating the process of clearing minefields containing these devices. The New Republic, Imperial Remnant, and various planetary governments also employed Defenders.
During the Galactic Civil War, the Empire enforced a blockade on the mining planet of Berason utilizing Defenders, a consequence of its unfavorable political alignment. Being a technologically underdeveloped world, Berason depended on external trade for essential food and medical provisions. As the blockade persisted, the inhabitants of Berason experienced a decline in health, thereby diminishing their resistance against the Empire. General Airen Cracken spearheaded a relief operation to deliver vital supplies to the planet, necessitating the navigation of the minefield. Equipped with vacc-suits and jetpacks, Cracken dispatched personnel to establish a corridor through the Defender network, wide enough to accommodate the incoming convoy.
Subsequently, following his ousted departure from his capital, Moff Kentor Sarne sought refuge in the Kathol sector, making a stop at the planet Shintel to replenish supplies and augment his forces. Upon his departure from Shintel, Sarne marooned the remaining troops by destroying their [hyperspace](/article/hyperspace-legends]-capable vessels and droids, and subsequently deployed Defender ion mines in the planet's orbit. Later, a section of this minefield was cleared by the New Republic CR90 corvette FarStar.