The Swiss Guard, the Pope's personal army of mercenaries and an unlikely relic of Europe's troubled, war-torn past, yesterday celebrated its 500th anniversary.
It will be a birthday party to remember. There will be a cascade of ceremonies over the next few months, culminating in a mass celebrated by Pope Benedict XVI himself on May 6, the day each year when new recruits are admitted to the world's smallest and oldest standing army.
The commemorative festivities will begin in the Sistine Chapel yesterday with a mass for the 110 members of the Pontiff's guard, presided by the Vatican's Secretary of State, Angelo Sodano.
Later the same day a 70-strong honor guard, decked out in their medieval military costumes of blue, red and yellow, will receive the Pope's blessing in Saint Peter's Square. This event reenacts the moment five centuries ago when the first contingent of 150 Helvetian soldiers - renowned for their fighting prowess - passed through the Porto del Popolo and into the Vatican, where they were blessed by Julius II.
Ever since then, the requirements for joining this elite force have been almost the same: "I am a Swiss citizen, a Roman Catholic faithful, of good moral ethical background, between 19-30, at least 174 centimeters tall, and not married," reads a partial list addressed to potential applicants.
On April 7, a contingent of ex-guards from Switzerland will begin a four-week "march toward Rome" along the same route taken by their military forebears, arriving in time for the swearing-in ceremony presided over by Benedict XVI.
The attendant parade usually takes place in the San Damasco Courtyard, but this year will be in St Peter's Square for the first time.
Driven from their impoverished, Alpine cantons in the 15th and 16th centuries, thousands of young mercenaries enrolled in the armies of the fiefdoms, kingdoms and city states that were constantly at war in France, Italy and Germany during the early Renaissance.
The Swiss Guard's greatest moment of glory was probably on May 6, 1527, when all but 42 of 189 soldiers died fighting off the armies of Charles V, which attacked and overran the Vatican.
The surviving guardsmen ushered Pope Clement VII to safety via a hidden passage.
Famous for their colorful uniforms and medieval weapons, guards don civilian clothes as part of the Pope's security detail when he travels.
The Swiss guards work side-by-side with another security force, the pontifical police.
It is not always a easy relationship: the police, charged with protecting the Vatican state, are Italian and know the place inside out. Most Swiss guards do not speak Italian, and have little opportunity to learn it.
Indeed, their limited mobility and strict requirements about sleeping in their quarters mean that the most potent enemy they face is often boredom.
Swiss guards serve for a minimum of two years, renewable up to 25 years.