A Chicago Daily Tribune article from 1927 has a story where Pershing had prisoners from the Moro Rebellion in the Philippines. The Moros were Muslims who resisted American or any other occupying force.
The Moros had swordsmen, called Juramentados, who were killing Christians in this uprising. It had to be stopped. General Pershing was given this difficult task.
The Tribune article says Pershing sprinkled some prisoners with pig’s blood, which the Juramentados believed would condemn them for eternity. But then Pershing let the prisoners go. He issued a warning to others about being sprinkled with the pig’s blood. The Tribune article said “those drops of porcine gore proved more powerful than bullets.”
There were no executions as described by Trump.
In fact, Pershing was more inclined toward peace talks with the Moros rather than violence.