UNSC Army

The UNSC Army  is a branch of the UNSC Defense Forces primarily responsible for land-based military operations.

Background
Little is known about the UNSC Army. This may be due to the fact that the Army is a land based fighting force, and thus none of the Army is assigned to naval battle ships, with the exception of transport by landing ships for planetary assaults.

The Army is a land-based fighting force. It is just as efficient as the Marines but are used in more conventional roles. The UNSC may have needed a faster, more mobile fighting force like the Marines to hunt down the rebels. They also may have different weapons such as the Rhino battle tank.

Ranks
Since all of the other branches within the UNSC (Navy/Marines) it is therefore reasonable to assume that the UNSC Army ranks are not changed from today's modern U.S. Army ranks:

ENLISTED RANKS:

Private (Recruit in Training) Private-PV2 Private First Class-PFC Specialist-SPC Corporal-CPL Sergeant-SGT Staff Sergeant-SSG Sergeant First Class-SFC Master Sergeant-MSG or First Sergeant-1SG Sergeant Major-SGM or Command Sergeant Major-CSM Sergeant Major of the Army-SMA (if rank still exists)

OFFICER RANKS:

Warrant Officer 1-WO1 Chief Warrant Officer 2-CW2 Chief Warrant Officer 3-CW3 Chief Warrant Officer 4-CW4 Chief Warrant Officer-CW5 Second Lieutenant-2LT First Lieutenant-1LT Captain-CPT Major-MAJ Lieutenant Colonel-LTC Colonel-COL Brigadier General-BG Major General-MG Lieutenant General-LTG General-GEN

Trivia

 * While no Army units have been identified, Tango Company might be one. Its members are referred to as soldiers, not Marines. Plus, its members show a very un-Marine like lack of discipline. However, until further information is revealed, it is assumed that Tango Company is a Marine unit.
 * The only known member of the UNSC Army is Colonel James Ackerson, an intelligence officer who was once an infantryman. He is seen in an Army dress uniform.
 * A joke among members of the Halo community is that the UNSC actually has two Armies, Red and Blue. This is a reference to Red vs. Blue, a popular Halo machinima.