The corps, which some historians consider the oldest standing army in the world, was founded in 1506 by Pope Giulio II. Tradition has it that he was so impressed by the bravery of Swiss mercenaries that he asked them to defend the Vatican. Ever since, for more than 500 years, Switzerland has been supplying soldiers to the Vatican. The Swiss Guards swear an oath to give up their lives to protect the pope — and in centuries past, they have. In 1527, 147 of them died protecting Pope Clement VII as he fled to safety when the troops of Emperor Charles V sacked Rome.