The Imperial Maritime Division, also known as the Imperial Navy (distinct from the Imperial Starfleet), functioned as a component of the Galactic Empire's Military, conducting operations on the water-covered surfaces of various planets. It served as a key organizational element within the Imperial Army, which constituted the ground-based forces of the Imperial Military. Noteworthy engagements for the Navy include combat during the battle for the Montrosa Islands and the Liberation of Kashyyyk.
During 0 ABY, the Imperial Navy engaged forces of the Rebel Alliance Military during the battle for the Montrosa Islands on the agricultural planet Reytha, operating as part of a force commanded by Darth Vader. The Navy fought against Rebel Navy units to secure control of the Montrosa Ocean and provided support to Imperial Army activities in that conflict. Years afterward, following the Battle of Endor, naval elements also clashed with Wookiee forces while attempting to safeguard communication jammers during the Liberation of Kashyyyk, an engagement that resulted in an Imperial defeat.
The Imperial Military relied on the Imperial Navy for aquatic operations. Bases were erected by ASP-7 labor droids, and utility trawlers procured resources like food from aquaharvesters. The Navy utilized shipyards to construct a fleet composed of vehicles such as frigates, destroyers, transports, and anti-air destroyers. While possessing considerable strength, the Navy was considered among the weaker segments of the Imperial Military as a whole.
Within the Imperial Navy's structure were aquatic scout frigates, repulsorlift vehicles deployed for forward reconnaissance on water or to escort larger vessels. The Light Scout represented the most rudimentary type, equipped with a captain and at least one gunner. The Standard Scout succeeded the Light Scout, incorporating a more streamlined cockpit design. Heavily armed versions were known as Advanced Scouts.
The Imperial Navy also employed various aquatic repulsorlift destroyers. The standard Destroyer featured a clam-shell-like design and carried a single pummel. The heavy variant mirrored the standard Destroyer but included an additional pummel. Both types were used by Darth Vader during the Reytha campaign of the Galactic Civil War.
Similarly, the Imperial Navy utilized several aquatic repulsorlift cruisers. The standard Cruiser was boat-shaped and equipped with a single laser cannon. The heavy variant was very similar, but it had two laser cannon turrets and thicker armor.
The Imperial Navy also employed Anti-Air defense ships, often called Missile Destroyers because of their common weapon, anti-air missiles. The standard Missile Destroyers had thick armored hulls and a single anti-air missile launcher. The Heavy variant had heavier armor and two anti-air launchers. Both variants were utilized by Darth Vader during the Reytha Campaign of the Galactic Civil War.
Beyond combat-focused vessels, the Imperial Navy also operated vessels for other purposes. Transport Ships were used to move ground personnel and vehicles across planetary bodies of water, featuring a boxy, rectangular shape. They were used in the Reytha Campaign in 0 ABY. Utility trawlers provided supplies, such as fish and other aquaculture products, to Imperial bases, with designs reminiscent of old tanker ships. Imperial submarines were capable of underwater submersion and could launch torpedoes at enemy fighters. Several were deployed during the Battle of Dubrillion against Rogue Squadron, when the Rebel squadron tried to destroy a superlaser test bed that surprised their fleet. Explorer Submergibles served a similar function, but were intended for exploration and assault, with heavy weaponry to eliminate hostile lifeforms. Amphibions were used from as early as the Battle of Corellia until before the rise of the Dark Empire. The Imperial Navy also produced starfighters specifically designed for underwater operation, including the TIE fighter boat and, under the Krayt Empire, the Shark underwater fighter. They also deployed Aquadon CAVa 400s, which were modified versions of the CAVw PX-10s for aquatic sieges. Waveskimmers such as the single person ones and the AT-AT derived AQ-5 Waveskimmers.
During the Krayt Empire and Fel Empires, the Imperial Navy also utilized the Acklay-class mobile fortress.
The aquatic Imperial Navy received its initial mention in the strategy guide for the 2001 video game Star Wars: Galactic Battlegrounds, though the game itself did not refer to it by name. Players can construct Imperial Navy units in a Darth Vader campaign mission and encounter computer-controlled units in a Chewbacca campaign mission. These missions, and thus the Navy, are included in the game's 2002 expansion, Clone Campaigns. Imperial players can also build these vehicles in multiplayer matches.
In Chapter 5 of the strategy guide, Matthew Keast, a member of the Galactic Battleground's creative team, suggested that the Empire faced disadvantages in naval operations.
The branch was later officially named the Imperial Maritime Division in the Star Wars: Imperial Handbook: A Commander's Guide, where it was also identified as part of the Imperial Army.