Despite their theological differences, colonial Americans shared a singular doctrine about the nature of religious faith: It could not be imposed by force but must be embraced freely by the mind and conscience of the believer

On Sunday morning, Jan. 21, 1776, at a church in Woodstock, Va., Rev. Peter Gabriel Muhlenberg brought his sermon to a dramatic and unexpected crescendo. His text was taken from the book of Ecclesiastes. “The Bible tells us ‘there is a time for all things,’ and there is a time to preach and a time to pray,” said Muhlenberg. “But the time for me to preach has passed away; and there is a time to fight, and that time has now come.”

Stepping down from the pulpit, the minister took off his clerical robes to reveal the uniform of a colonel in the 8th Virginia Regiment of the Continental Army. He had been personally recruited by George Washington. Outside the church door, drums sounded as men kissed their wives goodbye and strode down the aisle to enlist. In less than an hour, 162 men from Muhlenberg’s congregation joined the patriot cause.

The “fighting parson” was a common sight in the American Revolution. Why? Because American Christianity—anchored in a Protestant understanding of religious freedom—gave its blessing to democratic self-government.

For many evangelical ministers, unconstrained British rule not only represented an oppressive monarchy that trampled on their civil rights. It supported a national church, the Anglican Church, which they feared would impose its doctrines and practices on the colonies if given half a chance. As dissenting Protestants, American churchmen were as passionate about religious liberty as they were about republican (or “Whig”) political principles. “By combining Whig political theory with religious doctrine,” explains historian James Hutson in “Religion and the Founding of the American Republic,” “the preachers forged an especially powerful weapon to mobilize opposition to British policies.”

[Editor’s note: This article is incomplete. The source for this document was originally published on online.wsj.com—however, the original URL is no longer available.]