VATICAN CITY — For years, nuns around the world have worked to help trafficked and enslaved people break free from the conditions that ensnare millions of men, women and children.

They have prayed for them, and they have offered hospitality. On Sunday, they marched on St. Peter’s Square for them.

“There have never been as many slaves in the world as there are today,” Gabriella Bottani, the international coordinator of Talitha Kum, a global network of nuns that assists trafficked persons, said in kicking off the march. “Only together we can break the chain of trafficking and slavery.”

Dozens of nuns, lay people and a smattering of priests walked along the broad avenue that links the Castel Sant’Angelo to St. Peter’s Square, but Sister Bottani said that several women who had been trafficked decided at the last minute not to join.