Simplify the following text for a Grade 9 native English-speaking person.
Original: They had however been reinforced by a detachment of 32 grenadiers from one of the Swiss mercenary regiments summoned to Paris by the King shortly before 14 July .
Simplified: There was also an extra group of 32 grenadiers from one of the Swiss mercenary regiments brought to Paris by the King shortly before 14 July .