You're thinking of the infantry, considered the backbone of the Army.
Going infantry out of boot forts training options is a challenge, but it is also the gateway into more advanced fighting career fields such as Airborne Units, Ranger Battalions, Special Forces, Pathfinder, and Sniper School. The Army infantry motto is "Always Ready to Defend.
The Army does not offer a guaranteed job for any specific infantry MOS; the "X" means that the specific job is not known at the time of enlistment. You must earn a slot to the infantry during your training.
Detachment 1 produces over 1, mission-ready Airmen graduates annually.
During the training, recruits are allowed to list their specific infantry job preferences, but ultimate assignments are determined by the needs of the Army at the time. Infantry soldiers are trained in and use small arms, anti-armor or indirect fire weapons mortars during combat missions.
During training, soldiers will list their specific infantry job preferences, of which there are two: Infantryman 11B Indirect Fire Infantryman 11C The Army expects infantry soldiers to possess tremendous discipline, be ready to accept challenge and face danger, have an interest in light weapons and ground tactics and have the ability to remain calm under stressful situations. The infantry is equally important in peacetime and in combat.
The Infantryman's role is to be ready to defend our forts training options in peacetime and to capture, destroy and repel enemy ground forces during combat.
They fire and recover anti-personnel and anti-tank mines, which they locate and neutralize as well. These soldiers also engage targets using night vision sights, and operate and maintain communications equipment.
Since they are the first line of defense, these soldiers may be called upon to operate in nuclear, biological or chemical NBC contaminated areas.
And they construct field expedient firing aids for infantry weapons. Typically more soldiers will be 11B as there is usually a greater need for them. They are riflemen as well but operate in smaller platoons so likely will not be part of kicking down doors. However, if the 11C is assigned to a light Infantry unit there is more opportunity to be used as a rifleman as well as the Indirect Fire Infantryman.