the pen is mightier than the sword
"The pen is mightier than the sword" means  a person can cause people to change their opinions(e.g., to fight a war)and on a large scale whereas a sword can only change a peron's opion by force and then often only results in the person's death.
The Founding Fathers of the United States of America considered the pen to be mightier than the sword, and therefore were able to gain the freedom of America by uniting the colonists.