I haven't seen 'The Patriot' in recent years, so my memory is pretty spotty on that section, but I do know who the character of William Tavington, Jason Isaacs character, was inspired by, or based on - Banastre Tarleton. The short answer is that, yes, it does seem that brutality of the nature you described (Killing wounded patriots and slaughtering surrendering forces) did occur during the war. Though, while some elements of the movie was exaggerated heavily for dramatic effect, other elements stayed true to history - however, I do not know of any children that Tarleton or his men has personally killed, nor do I have any knowledge of him burning a church filled with innocent civilians. Since the primary cause of Tarleton's infamous actions occurred on the battlefield, which was not exactly a place for children or innocent individuals, I find it hard to believe he might've had a hand in killing children. The individuals wounded in the primary battle that I'll be focusing on were however taken to a church, the Waxhaws Church, where a young Andrew Jackson helped alleviate the suffering of the wounded, together with his family.

To understand the massacre that occurred at the Battle of Waxhaws, you have to understand the circumstances that allowed it to happen, and who the man at the center of it was. Tarleton was a merciless commander, an excellent officer, and a daring strategist. He had started out in the British army in just 1775, and had propelled himself up the ranks from the lowest commissioned rank to Lieutenant Colonel in barely three years. He had fought with distinction during the campaign for New York, aiding in the capture of General Charles Lee, which was part of his dazzling rise through the ranks. Robert D. Bass & John Ferling describes Tarleton as: "... Stocky and powerful, with sandy red hair and a rugged visage that disclosed a hard and unsparing nature, Tarleton had the reputation of one who was anxious of every opportunity of distinguishing himself.".

Tarleton helped support the siege and capture of Charleston together with Sir Henry Clinton, and part of his role during the siege was to cut off the avenues of escape that Continental Commander Benjamin Lincoln might use, and one such escape route would've been Monck's Corner, which Tarleton assaulted, and took, on the night of April 14^th, 1780. It was after this battle that many of the Continental Officers posted at the Corner took flight, and escaped in to the surrounding swamps, soon to be joined by the scattered remnants of Lincoln's army (including Continentals, and North Carolina Militiamen) after the fall of Charleston. Three days after the fall, on May 15^th, 1780, General Clinton learned of the retreating forces and their destination, and ordered Lord Cornwallis to stop them before they escaped completely. Cornwallis' army, however, was far too slow to keep up with Buford's much smaller force, and so on the 27^th, Cornwallis dispatched Tarleton and 270 men to catch up with them.

Tarleton's Legion covered 160 miles on horseback in just two days to catch up with the retreating forces, and in their tracks was a line of dead horses, ridden to exhaustion and left on the wayside. When they caught up to them, it was May 29^th, 1780. The Continental Commander, Abraham Buford, had no real artillery to defend himself against the enemy, as he had sent them on ahead with the baggage. He did, however, outnumber Tarleton's force two to one, but opted for a single heavy thunderous volley to take down and stop the oncoming cavalry charge. It failed, and Tarleton's cavalrymen got deep in to the lair of the enemy, and destroyed any kind of resistance the Rebels might've hoped to put up. Limbs were severed, skulls were crushed, bodies were decapitated, and the Rebels were being massacred. Tarleton failed to stop the ensuing onslaught, as he had been trapped early on in the battle under his dead horse. His soldiers believing him shot dead during a truce, fought on with a determined fury. Tarleton, however, didn't order the slaughter, but he didn't stop it either, and this wasn't the first time he failed to control his men and uphold discipline. The Rebels screamed for Quarter, but none were given. The Loyalists waded among the wounded Rebels 'hacking and bayoneting in a saturnalia of bloodshed.' - It was a veritable massacre. 'Tarleton's Quarter' was later used as an expletive by the Americans. Tarleton himself said in his report '... I have cut 170 Off'rs and Men to pieces'. Ferling mentions that '... In a war in which rarely more than 6 or 7 percent of combatants fell on a battlefield, nearly 75 percent of the Virginians fell victim on this day of horror in the Waxhaws.'.

The Battle of Waxhaws, Buford's Massacre, had concluded - the fighting itself was over in seconds, but the bloodshed continued for a while. The Continental Congress used the battle as a heavy-hitting propaganda tool to drum up support, incite rage against the British empire, and to recruit new soldiers in to their ranks. South Carolina, having once lost their capital, began to fight back, with the Battle of Waxhaws being one of the primary reasons.

Sources (& suggested reading):

[1] John Ferling's 'Almost A Miracle'

[2] Robert D. Bass' 'The Green Dragoon'

[3] Walter Edgar's 'Partisans & Redcoats'

[4] Robert Allison's 'The American Revolution: A Concise History'

[5] John R. Alden's 'A History of the American Revolution'

I was beat to the punch!

I very much agree with u/zuzahin. Just to add a little:

This is an excellent question and before I go any further, let me first recommend a wonderful new book on this very subject. Holger Hoock’s Scars of Independence lays out how brutal the American Revolution was in many places. It’s important to remember that at its core, the American War for Independence was in many ways a brutal civil war. As John Adams figured at the time, the nation was probably roughly 1/3 patriots, 1/3 loyalists and another 1/3 indifferent. Historians have demonstrated that many of these “indifferent” colonists really supported whoever held the upper hand in their region. In many towns, especially in the colonial interiors, you had competing Tories and Patriots waging brutal battles against each other that don’t make the American history textbooks. Certainly battles like Cowpens in SC (depicted in The Patriot) and Bunker Hill in Boston could be brutal, especially in the hand-to-hand combat that took place in close quarters, these local skirmishes between militias could pit family members against each other and neighbors against neighbors with the losing side often being forced to flee their homes, sometimes forever. I’m currently doing research in Nova Scotia and reading a lot of loyalist testimonies and they are full of really interesting descriptions. Often times, Patriots would come to Tories homes in the middle of the night, ransack the home, and threaten the lives of the entire family forcing them to flee to the nearest British government establishment, which in some cases could mean days of travel.

Patriots were not the only aggressors. Hoock’s book emphasizes the battles that took place on Long Island, New York, and New Jersey as being particularly brutal. Advancing British soldiers were notorious for ransacking homes of Patriots, Tories, and “neutrals” alike. Often recruited from the lower dredges of English society, these soldiers plundered, raped, and murdered their way across the middle colonies. In addition, thousands of Patriots and suspected Patriots languished on prison ships in the New York harbor and in Halifax where many died of starvation and other diseases.

In The Patriot, Isaacs' character Cornel William Tavington is based on notorious Lt. Cornel Banastre Tarleton. Isaacs’ character; however, is greatly exaggerated. The scene where Tavington locks the town’s people in the church and burns it to the ground is not based on any real recorded situation. What the film does do well (and it doesn’t do much well, especially the whole slave component who “love” their master and his children) is depict the Revolution in the South. Most Americans associate the war with New England, but the war in the South was likely more brutal as the civil war raged between neighbours.

Finally, Hoock’s book makes an excellent point about why the Revolution is not remembered as especially violent. He argues that unlike the Civil War, where many of leading names including Lincoln himself, died, all the major leaders of the American Revolution escaped with their lives. This means that in American memory, the Civil War overshadows (probably rightly so) the American Revolution in terms of brutality.

For more readings I would suggest:

Holger Hoock’s Scars of Independence

Carol Berkin’s Revolutionary Mothers

John Ferling’s Almost A Miracle

Andrew Jackson O’Shaughnessy The Men Who Lost America

Clauido Saunt West of the Revolution

I'd like to expand a bit on the very good answers /u/zuzahin and /u/irishpatobie a bit by looking at the war in the West between the American revolutionaries and Native Americans, particularly the Six Nations of the Iroquois. Starting slowly in 1775 and 1776, this became one of the bloodiest theaters of the war, marked by the specific targeting of civilians by both sides and the routine destruction of towns.

The biggest single campaign launched against the Indians during the Revolution was the Clinton-Sullivan expedition, during which Washington tasked Continental troops with the utter destruction of Iroquois Country. This expedition was prompted by several Iroquois and loyalist raids into the Wyoming. Mohawk, and Cherry Valleys, killing hundreds of American soldiers and civilians. Immediate American reprisals at Unadilla and Onaquaga inflicted comparably indiscriminate damage, but the Washington and the Continental Congress wanted something more systematic.

It's worth it to take a look at Washington's orders to Major General John Sullivan (emphasis added)

The Expedition you are appointed to command is to be directed against the hostile tribes of the Six Nations of Indians [the Iroquois], with their associates and adherents. The immediate objects are the total destruction and devastation of their settlements, and the capture of as many prisoners of every age and sex as possible. It will be essential to ruin their crops now in the ground and prevent their planting more. I would recommend, that some post in the center of the Indian Country, should be occupied with all expedition, with a sufficient quantity of provisions whence parties should be detached to lay waste all the settlements around, with instructions to do it in the most effectual manner, that the country may not be merely overrun, but destroyed. But you will not by any means listen to any overture of peace before the total ruinment of their settlements is effected. Our future security will be in their inability to injure us and in the terror with which the severity of the chastisement they receive will inspire them.

Elsewhere, Washington stated that American soldiers should refrain from scalping and torturing British soldiers and white loyalists they captured in Iroquois country, with the caveat that such protections did not apply to Indians who did not follow the accepted rules of war.

Washington god his wish. American forces burnt their way through Iroquois country, driving nearly the entire surviving population towards the British as refugees. The torture and execution of prisoners was common on both sides. At one point, soldiers of the Third New York Regiment boasted of making themselves new leggings from the hides of captured Indians. Washington, who was never actually present on the expedition, remains known in Iroquois lore as the Town Destroyer.

Sources: John Martin and Joseph T. Glatthaar, Forgotten Allies: The Oneida Indians and the American Revolution

Bereleth, Bloody Mohawk