The Marine Corps consists of two regiments (both founded in LY 903), though since 913, they have been separate organizations. The Marines of First Sea are commanded by Commandant Gilbert Tridentwielder; headquartered in Neptune's Deep. The Marines of West Ocean are commanded by Brigadier Selena Noriharvest; headquartered in Nautica.
The Marine Corps is the military force of the merfolk. It was organized in LY 903, to offer help to the navies being organized at the time by the Protestant Movement, to fight the Coming of the Order. However, following the war, the Marine Corps was incorporated into the military forces of the Second Order (the country which came to be known as First Nation in 914), along with the Army and the Navy. Following the Secession Referendum of 913, the two regiments of the Marine Corps separated when the citizens of West Ocean voted for sovereignty. However, both organizations retain the name "Marine Corps."
From the time merfolk were first created in 810, they have often had skirmishes with kappa, which had been created in 579. In 910, merfolk formally declared war against the kappa, though the details of the war and what specifically triggered it are unknown. Assistance against the kappa was offered by the Navy, though the merfolk declined, considering the matter their own problem, in spite of the fact that kappa have posed a threat to humans over the centuries as well, even before the merfolk existed. The Corps took little part in the Chaos War of 912.
- Commandant¹: Head of the Marine Corps; commands all regiments.
- Brigadier²: Commands a regiment of 2 or more battalions; 540 or more seamen.
- Major: Commands a battalion of 3 companies; about 270 seamen.
- Captain: Commands a company of 3 platoons; about 90 seamen.
- Lieutenant: Commands a platoon of 3 squads; about 30 seamen.
- Sergeant: Commands a squad of about 10 seamen.
- Seaman: Lowest rank in the Marine Corps.
1. The head of the Marine Corps was originally known as the Commandant, and under him, each regiment was headed by a Brigadier. Following the separation of the regiments in 913, the Marines of First Sea continue to be headed by a Commandant, though for the time being the position of Brigadier has been eliminated. (The First Sea regiment was formerly commanded by Brigadier Hanna Botanical.)
2. The Marines of West Ocean eliminated the position of Commandant in 913, with the Brigadier now being the highest rank.
It is expected that the respective corps of both First Nation and West Ocean may eventually reinstate the positions which have been eliminated, if and when each organization establishes new regiments.