Wikia

The tactical officer or weapons officer is responsible for co-ordinating the operation of a starship's weapons and defensive systems.

Klingons call their tactical officers the "weapons officer".

Starfleet (23rd century)Edit

On 23rd-century ships, the tactical officer managed phaser and torpedo crews who wore command gold. On explorers like the USS Enterprise, the role of tactical officer was generally combined with another post, reflecting the expectation that combat would not be an everyday task. Helm officer Hikaru Sulu and navigators such as Pavel Chekov acted as tactical officer during the original five-year mission. On the USS Exeter, Paul Cutty doubled as security officer and tactical officer, with a station forward and portside of the captain's chair. On the USS Farragut, Henry Prescott III similarly combined security and tactical roles. Both further de-emphasized their tactical role by wearing security red rather than command gold. (TOS, Starship Exeter, Starship Farragut)

Warships such as destroyers naturally gave more prominence to the post of tactical officer. For example, USS Tamerlane's tactical officer and first officer, Angelica Bennett. (Tamerlane)

By the 24th century, the tactical officer position was generally combined with the security chief position, such as Luko on USS Excelsior and Maya Stadi on the USS Odyssey. They wear security yellow, not command red. They typically have their station aft of the captain's chair. (Star Trek: Hidden Frontier, Star Trek: Odyssey)