Theseus-class light carrier

The Poseidon-class light carrier (hull classification symbol: CVL) is a carrier classification in service with the UNSC Navy. Cheap and easy to construct, the Poseidon was first introduced in the immediate months following the end of The Great War in an effort to fulfil a sorely-lacking need for fighter carrier craft in the battered Navy. The initial batch of Poseidons were constructed by Martian Metals Shipyards in the surviving shipyards over Mars and Ganymede, as well as the mostly-untouched shipyards in the Jovian lagrange points, utilising many components of existing UNSC frigates and destroyers salvaged from the destroyed battlegroups throughout the system.

These initial specimens were used by the UNSC to fill the need for strikecraft carriers in the Navy. With the destruction of almost the entire reserve of larger carriers such as the, and  in the Fall of Reach and Sol campaign, the needs of force projection for reasserting UNSC control over the Human Sphere were sorely lacking. As the Navy's fleets were slowly rebuilt throughout the ensuing decades, the Poseidon's role gradually shifted from bearing the brunt of force projection to one of conducting patrols and fleet support duties across the board. Some ships were eventually relegated to back-line logistical support duties, or sold to regional colonial guards as their need diminished.

Development
The battles of Sol and Epsilon Eridani in the final months of the war with the Covenant saw the UNSC fleet decimated, and the Navy's carrier loadout decimated to only a handful of surviving vessels. As such, the fleet found itself with a critical shortage of carriers for strikecraft projection, and the barely-operational status of the remaining major shipyards meant that larger ships like the Epoch and Punic would still be multiple years from coming online. As such, the Poseidon was created by the naval architects of Martian Metals Shipyards with a focus on easy and cheap construction with fast turnaround times. The ships were designed to use many parts shared with existing ship classifications, with an intent to reuse many of the salvaged parts found in orbit across the Sol system to reduce costs. These early ships were built on the same core hull framework as Martian Metals' Eligus civilian freighter class, with the initial batch of ships converted directly from existing Eligus-class ships or built off some existing half-constructed Eligus hulls. The initial production run of Poseidons were initially termed the Poseidon-class escort carrier and given the hull classification CVE.

Between 2553 and 2557, 56 Poseidon-class escort carriers were constructed over Mars and Ganymede, using many salvaged parts and an attitude of "waste not, want not" in regards to construction. As such, these early ships were often termed "frankenships" and had very little standardisation due to resource availability issues. These ships were used in the early post-war years to serve a vital force projection role as the UNSC began to expand its reach back into the colonies, serving as a slipspace-capable platform from which fighters, troops and dropships could be rapidly deployed without the additional baggage of larger ship classes such as a MAC.

In 2557, Martian Metals introduced a new schema for Poseidon construction to standardise all future Poseidons, and the class was reclassified by the UNSC Navy as the Poseidon-class light carrier (though existing extreme frankenship examples retained the escort carrier nomenclature). The validity of keeping the Poseidon in service was repeatedly called into question in several naval reviews throughout the late 2550s and early 2560s, though the Poseidon's ability to keep up with destroyer wolf-pack task forces ultimately provided it a valuable niche, allowing it to remain relevant as the UNSC Navy began to overhaul its fleets from the war-era standard.