VALLEY FORGE, Penn. -- Even though Americans celebrate Independence Day each year, it's sometimes easy to forget the depth of a word like "liberty."
Men fought and died so America could be free, but for them liberty was intertwined with the God of liberty.
It's a sad fact of history: Christians fleeing the Old World to practice their own religion often turned right around and persecuted fellow Americans from other denominations.
They wanted theirs to be the recognized state church, ruling over all others. But watching that persecution outraged future leaders like James Madison.
"As late as the early 1770s, you have Baptist preachers who are getting thrown in jail for illegal preaching in Virginia," Thomas Kidd, author of God of Liberty, said. "And James Madison as a young man watches this going on, and he thinks its despicable."
Thomas Kidd writes that these future revolutionary leaders began to see religious liberty, indeed liberty itself, as a basic God-given right for all. They saw that defending it was a crucial duty to the God who created them all and created them free.
"People like Jefferson and Madison make common cause with these evangelicals, especially Baptists, on the issue of religious liberty," Kidd said.
When England began to push the colonies around, the colonists worried it would first take their economic freedom, but then, more importantly, their religious freedom.
They'd demonstrate against taxes. But for liberty, they'd be willing to fight and die in a revolution.
"Taxes were sort of the spark that ignited it, but the issue was far greater than whether you were going to have to pay more taxes or not," Rod Gragg, author of Forged in Faith, said.
"They believe that the attack on their economic rights was actually a precursor to an attack on their religious rights," Kidd said. "And they believed that religious liberty was the most precious liberty. And if they didn't act in 1775 and '76 -- that ultimately they would lose all their rights."
"Americans at the time believed in higher law, that God's law was over everything, over man's law," Gragg said.
Gragg added that Christian Americans believed England was going against God and His law in crushing their God-given rights.
"They believed that their first obligation was to God," Kidd explained. "And that if a government tried to intrude on that, that gave them the right, the liberty to revolt against that government."
In fact, they saw it as their duty to God.
"'Rebellion to tyrants is obedience to God.' This was a favorite saying of Jefferson and also of many evangelicals," Kidd said.
The men who fought the battles of the Revolution and endured harsh winters in places like Valley Forge weren't just fighting for their rights and concepts like freedom and liberty. They were fighting for someone.
Of course, for their fellow Americans, but also for the God of Liberty.