For infantrymen earning an Expert Infantryman Badge shows they are at the pinnacle of their military occupational specialty skills. It is not an easy task, but rather arguably one of the most difficult in the Army to achieve.

Infantrymen from across Fort Jackson, and from as far away as Fort Irwin, California, have been testing their MOS proficiency since March 19 as they try to earn the right to wear the EIB.

The EIB is different from the Combat Infantryman Badge because any infantryman in direct armed contact with the enemy is awarded the latter, while they must be tested to be called experts.

Sgt. 1st Class Patrick Young, a senior drill sergeant with Delta Company, 3rd Battalion, 39th Infantry Regiment, said the EIB is must have to become a senior non-commissioned officer in his career field.

"It's very important," he said. "From a MOS proficiency standpoint it's a key thing for us to have. We actually receive a lot of training to standard that we don't typically get out on the line -- (common task training)-oriented, book answer stuff we don't learn that often.

"As for a promotion it's fairly difficult to become a sergeant first class and above (in the infantry) if you don't have an EIB. It's a big discriminator to being selected as a senior NCO."

For Pfc. Marco Salas, from 2nd Battalion, 11th Armored Cavalry Regiment at the National Training Center in Fort Irwin, going through the testing has been a pleasant surprise due to the cadre helping him during train up for the testing.

Salas said he was at Fort Jackson because "NTC doesn't have their own EIB (testing) anymore."

"The cadre is great here," he said. "They do a great job of explaining it. If you don't understand the task, they figure a way to simplify it" so you can better understand how to complete it properly.

Young, a grader for the react to direct fire task, earned his EIB in 2007 when he was at Fort Polk.

"When I was a younger pup and didn't know any better, didn't know what it meant; I just went out and trained on it" and got an EIB.

It wasn't as easy as that, he added.

"It's tough. I think historically it's been like 15 percent (of candidates) across the board every year" earn the EIB, Young said. "For some guys this is their fourth or fifth try at it … it's a tough task."

The EIB is difficult for candidates because messing up on an event can cause them to be disqualified. While the Soldiers can get a couple "do-overs" it depends on the event.

If they "no go" on any individual tasks "like rifle marksmanship or PT they're done," Young said. If the candidate messes up on an event they can get retested, but "if they double no-go any task or single no-go three different tasks they are done."

Some of the tasks seem simple, but luck can play a factor.

Young said hand grenades are some of the toughest because "there is a little luck there. If it lands on that fuse it can go any direction. You have to be a pretty skilled guy with a grenade to where you are, kind of, ruling luck out."

Salas, a rookie candidate said taking time to pay attention to the slightest detail pays off.

"The most difficult part of it for me is paying attention to detail," he said. "What usually gets people is that they forget something. You either get out of sequence or you catch it quickly so you don't get out of sequence. It pays to pay attention to detail."

Candidates will continue testing until Friday when they will face a daunting road march before being awarded the skill badge during a ceremony.