At the age of twelve, he left his parents and his younger sister to ease the burdens on his family and went to the nearby small town of Monpazier.

He led the same type of life at Agen, studying at the College of the Carmelites until the age of twenty, when he returned to Monpazier briefly,[1] before going to Lectoure.

In October 1353, Pope Innocent VI appointed legate to regularizing relations between the rival republics of Venice and Genoa.

[2] Dusan's goal was in fact to find political support in order to set out, under the cover of defense of the Catholic faith, to conquer Byzantium and its Empire.

In view of the complex geopolitical situation and the lack of honesty of the ruler of Serbia, this mission of Peter Thomas did not succeed, in spite of his efforts.

In April 1357, Thomas went as papal legate to Constantinople, to receive the submission of the Emperor of Byzantium to the Roman Catholic Church in exchange for military support of the West to block the expansion of the Ottoman Empire.

Philippe de Mezières wrote: "Physically involved in the battle, Pierre Thomas stimulated the troops: it was necessary to avoid a stampede [in front of the janissaries].

Between defeats and victories, Pierre Thomas was "tireless, leading the troops into battle by his example and his exhortations, sometimes in Smyrna, sometimes in Rhodes, sometimes in Constantinople, sometimes in Cyprus, sometimes in the island of Crete, and sometimes in Turkey with a few galleys".

At Christmas 1359, Thomas was in Rhodes and sick with a long illness but had recovered sufficiently by Easter to crown Peter I of Cyprus titular "King of Jerusalem".

They stopped in Avignon where Pierre Thomas explained his Crusade project to Urban V, whose official approval he obtained on 31 March 1363.

But this victory was short-lived because the crusader soldiers, motivated by the lure of gain, were seized with fear at the idea that the Saracens would come to the rescue of the besieged city, which they soon did.

The first is that Pierre Thomas caught a cold during the celebrations of the Nativity by living too austerely and without taking into account the rigors of winter, which caused a fever that led to his death11.

In Salles-de-Belvès (France), the small chapel erected on the presumed site of the saint's birthplace was destroyed during the French Revolution.

Before his death, Peter Thomas gave a relic of the Holy Cross to Philippe de Mézières, who, donated it to the Scuola Grande of the church of San Giovanni Evangelista in Venice.

Saint Peter Thomas is depicted in an altarpiece painted by Francisco de Zurbarán for the College of San Alberto, Seville, which is currently held by the Museum of Fine Arts, Boston.