They outlast every pope.

And after the Pope, they are probably the most photographed Vatican icons.

A total of 30 young men took an oath of allegiance as Swiss Guards on a sunny Tuesday, Vatican Radio reports.

On a bright Tuesday morning in the San Damaso courtyard of the apostolic palace 30 young men took a solemn oath of allegiance to Pope Francis accompanied by military pomp.

As new members of the Pontifical Swiss Guard they are an elite force who has been protecting pontiff's for centuries.

"Our core mission is traditional," say the Swiss Guards, on their website. "Since 1506 we protect the Pope and his residence. Our mission has not changed in over 500 years."

Recruits to the guards must be Catholic, single males with Swiss citizenship who have completed basic training with the Swiss military and can obtain certificates of good conduct.

Recruits must have a professional degree or high school diploma and must be between 19 and 30 years of age and at least 174 cm (5 feet 8.5 inches) tall.

Tuesday's swearing in ceremony took place in the presence of Vatican dignitaries, the new Swiss ambassador to the Holy See, Pierre-Yves Fux and Archbishop Giovanni Angelo Becciu, who is the substitute for General Affairs of the Secretariat of State.

"Five hundred and eight years have passed since the establishment of this meritorious Guard corps," said Archbishop Becciu, according to the Vatican Information Service, "and the fact that Switzerland continues to send young men keen to serve the Pope is a cause for offering fervent thanks to God."

In a speech, the Pontifical Swiss Guard's commander Colonel Daniel Anrig told the new recruits that they were swearing an important oath, Vatican Radio reported.

The colonel said the oath of the new recruits is "to serve the Supreme Pontiff faithfully, loyally and honorably and commit all their forces for him, even at the risk of one's own life, if necessary."

RECRUITING WOMEN

In 2009, Anrig suggested that the Guard might someday be open to recruiting women, but he noted that the admission of female recruits remained far in the future.

As part of the ceremony each new member placed a hand on the flag of the Swiss Guard and raised three fingers on their other hand, which symbolizes the Holy Trinity.

This event takes place every year on May 6 and it marks the most severe event in the history of the guard when in 1527, 147 members lost their lives while fighting Holy Roman Empire troops during what is historically known as the "Sack of Rome."

This battle allowed Pope Clement VII to escape to safety through a stone passageway leading from the Vatican to Castle Sant Angelo on Rome's Tiber river.

During their time in service as Swiss guards these men wear the famous blue, yellow and red uniform which is celebrating its 100th anniversary this year.

As well as protecting the Pope, the Swiss Guards answer tourists' queries and perform ceremonial duties as well as assisting at Vatican events.

The Associated Press reported the Swiss Guards legend was stained in 1998 by the slayings in a Vatican City apartment of the guard commander and his wife.

The AP said the Vatican blamed the first killings in the papal city in 150 years on a disgruntled guardsman who it says, then shot himself dead.