The armed forces of the Sith, known as the Sith military, served the Sith Empire during both the Jedi Civil War and the Sith Triumvirate throughout the Dark Wars and the First Jedi Purge.
The origins of the Sith military can be traced back to the Mandalorian Wars, where the Jedi Knight Revan was appointed as the Supreme Commander and given direct control over a third of the Republic Military. As the Mandalorian Wars progressed, Revan began to succumb to the influence of the dark side of the Force. During the decisive Battle of Malachor V, Revan deployed the Mass Shadow Generator to obliterate the Mandalorian fleet. This action also solidified his dominion over his forces, as a significant number of Republic casualties were among those not directly loyal to him. Following the war's conclusion, Revan's Republic forces accompanied him into the Unknown Regions. Officially, this campaign was aimed at eliminating Mandalorian Neo-Crusader remnants, but its true objective was to locate the Sith Empire, which had secretly reformed after the Great Hyperspace War and orchestrated the Mandalorian Wars.
After Revan and Malak's corruption by the Sith Emperor, they were tasked with finding the Star Forge. However, they rebelled, establishing their own Sith Empire and transforming their Republic forces into the Sith military.
Fueled by the Star Forge's almost limitless production capabilities, the Sith military possessed the necessary personnel and resources to launch a full-scale invasion of the Galactic Republic. The Battle of Foerost in 3959 BBY marked the beginning of the Jedi Civil War, during which the Sith military seized a substantial portion of the Republic Navy's fleet at the Foerost Shipyards. The defection of significant portions of the Republic Military to the Sith military facilitated rapid advances with minimal losses. The Czerka Corporation provided logistical support and materiel through an agreement.
In 3958 BBY, Admiral Saul Karath of the Republic Navy defected to the Sith Empire. One of his initial actions as a Sith admiral was to lead the Bombing of Telos IV. The orbital bombardment was unprecedented in its magnitude, resulting in millions of deaths and serving as a stark warning to the Republic about the Sith's willingness to resort to extreme measures. In 3957 BBY, Darth Revan was captured by the Jedi. However, Darth Malak attempted to assassinate his former master and assumed control of the Sith Empire and its military.
Following Malak's rise to power, the military strategy shifted from strategic conquest, with a focus on preserving industrial capacity, to a policy of total war. In 3956 BBY, the Sith military captured Taris and initiated an attack on the Republic Hammerhead-class cruiser Endar Spire in an attempt to eliminate Bastila Shan. After Revan, his memory erased and now serving the Republic, rescued Shan, Darth Malak ordered the destruction of Taris, resulting in the deaths of billions of citizens and shocking the galaxy.
Sith forces clashed with Revan during his search for the Star Maps during his raid on the Manaan Sith Embassy. Under Darth Malak's command, the Sith military launched an attack on Dantooine, conducting orbital bombardments and ground operations, destroying the Jedi Enclave and occupying the planet. Sith forces also briefly captured Revan before he escaped after killing Admiral Karath aboard the Interdictor-class cruiser Leviathan. Revan then proceeded to eliminate the Sith Academy on Korriban while locating the final Star Map. The Battle of Rakata Prime marked the end of the war, with Darth Malak's death, the Star Forge's destruction, and the fragmentation of the Sith Empire and its military. Widespread uprisings, such as the Ahto Uprising, erupted as worlds rebelled against Sith rule.
While the Sith Empire had splintered and various Sith lords and military leaders vied for power as their influence waned, some elements eventually united to form the Sith Triumvirate, led by Darth Traya, Darth Nihilus, and Darth Sion. Lacking Revan's overt power in terms of troops and resources, the Sith Triumvirate instead favored covert operations by Sith assassins to carry out the First Jedi Purge.
During the Conclave at Katarr, Darth Nihilus annihilated all life on the planet and killed numerous members of the Jedi Council. Sith forces under Darth Sion pursued the Jedi Exile Meetra Surik to Peragus II, destroying the critical fuel source for Citadel Station at Telos IV. Sith forces under Darth Nihilus also intervened in the Onderon Civil War on behalf of the Onderon separatists, initially covertly, and then overtly during the Second Battle of Onderon. Darth Nihilus then assaulted Telos IV with his remaining space and ground forces before being killed by Surik. The Battle of Malachor resulted in the final defeat of the Sith Triumvirate and the Sith military, with the deaths of Darth Traya and Darth Sion marking the conclusion of the Dark Wars and the First Jedi Purge in 3951 BBY.
The military's soldiers were commonly referred to as Sith troopers and wore silver armor and helmets that completely concealed their bodies.
Many of the Sith military's officers and enlisted personnel were former members of the Republic Army and Republic Navy who defected before or during the Jedi Civil War. Prominent senior officers included Admiral Saul Karath, who commanded the Sith military's space forces after his predecessor was removed for questioning Darth Malak's orders, Admiral Varko, who succeeded Admiral Karath, General Derred, and Mon Halan.