Despite their high-profile mission, many people, even those who serve in the military, have little idea what goes into becoming a member of this elite unit. That’s why the Pentagon Channel is devoting its latest half-hour “Recon” documentary to the 3rd United States Infantry Regiment -- the Army’s “Old Guard.”

The show will debut Dec. 29 at noon Eastern Time and will be repeated throughout January. It will also be available via podcast, vodcast and video on demand.

“We’re a very unique organization,” said Col. Robert Pricone, the 3rd Guard’s commanding officer. “We’ve got a very diverse mission set, and we operate in the very sensitive environment of the National Capital Region.”

The unit is one of the Army’s most challenging assignments to secure. “I tried three times to get in,” said Pentagon Channel News anchor Staff Sgt. Jake Newman, who once served with the Old Guard as one of the unit’s few broadcasters. Applicants must meet rigorous requirements. Men must be at least 5 feet, 10 inches tall, and women must be at least 5 feet, 8 inches. High scores on both general technical and physical training tests are also mandated. Once candidates are chosen for an Old Guard assignment, they must undergo a month of intensive regimental training.

“I’ve heard about it my whole life,” said Spc. John Ball, a watchman on the Old Guard’s Presidential Salute Battery. “It’s a prestigious unit, and I just wanted to be part of the best.”

The Pentagon Channel takes viewers inside the Old Guard’s headquarters at Fort Myer, Va., adjacent to Arlington National Cemetery, where the Regiment’s Caisson Unit ceremoniously transports caskets of fallen servicemembers to their final resting place.

“It’s just so much an honor, being the person to present that flag to that family,” said Command Sgt. Maj. Craig Robertson. “Knowing that that soldier that you are laying to rest has served this country well and gave so much for this nation, and to be part of that is so much an honor.”

The documentary exposes viewers to little-known facts about the Old Guard, such as that it is the only Army unit allowed to march with fixed bayonets. This Recon program also explores the regiment’s specialty platoons, who perform painstakingly meticulous missions and wear unconventional uniforms such as those originally designed by Gen. George Washington during the Revolutionary War era.

Pentagon Channel crews also were invited to tape sentinels at the Tomb of the Unknowns after cemetery visiting hours, when rules for keeping watch are much different from those in place when tourists are there during the day. Viewers will learn fascinating details about the stunningly precise rules Old Guard soldiers must follow as they perform their various duties.

The Pentagon Channel had the rare opportunity to videotape Old Guard service members as they practiced maneuvers under the extraordinarily demanding eyes of drill masters.

“Typically, we lose more than half the soldiers coming through the training cycle,” said Sgt. 1st Class Brent Thompson. “Every once in a while, you have soldiers that have the ability to pick it up pretty quickly and pick up on what we do, and some just will never get it.”

Pvt. Christopher Boovier, who is training to join the Old Guard, hopes he’s among that first group of soldiers. “I mean all the guys are cool, but if you can’t cut it, you can’t cut it,” he said. “I’m hoping that I get on. … Stuff happens sometimes, but I’m pretty confident.”