As a Dominican Friar devoted to a life of prayer, fasting and poverty, he called the princes of the Church back to a simpler and holier way of life – a message that was not well-received by bishops and priests who had become accustomed to the wealth, power and freedom they enjoyed while collaborating and reveling with the royalty of the day.

Pius was tireless in pursuing the broad reforms called for by the Church fathers. To address the lack of knowledge of faith among Christians, he created a new catechism and established the Confraternity of Christian Doctrine (CCD) for forming the young in the faith. He founded new seminaries for providing proper training for priests. To elevate the prayer life of the Church, he released a new missal and a new breviary. The 1570 edition of the Roman Missal he promulgated was used for 400 years, until Pope St. Paul VI revised it after Vatican II.

Pius also significantly changed the way the Church engaged the world. He built hospitals and provided food for the poor that had previously been spent for decadent papal banquets.

He ordered the building of public water and sewer systems in Rome that reduced the risk for spreading malaria and typhoid. Tradition reports that he spent his own money to import corn to feed the poor during a famine.

Pius successfully rallied the warring Catholic states to form the Holy League just in time to defeat the vastly larger fleet of the invading Ottoman Empire in the Battle of Lepanto on Oct. 7, 1571. He proclaimed Oct. 7 the feast of Our Lady of Victory, in honor of the Blessed Mother, whose intercession was invoked prior to the battle. The feast is now called Our Lady of the Rosary.

St. Pius was canonized in 1712.