The battle began with bad intelligence. Lieutenant General Wilhelm von Knyphausen, commanding the British garrison in New York City, had received word from spies that Washington's army at Morristown had been reduced by disease and desertion to just 3,500 men. Mutinies had eroded morale. Knyphausen saw a chance to deliver a mortal blow to the Revolution and believed the war-weary people of New Jersey would offer little resistance. His plan was straightforward: advance 6,000 men from Elizabethtown, seize the town of Springfield and Hobart Gap by sunrise, then push through the Watchung Mountains to hit Washington's main encampment eleven miles beyond. It was a sound plan built on a faulty premise - the people of New Jersey were not nearly as defeated as his spies had promised.

Knyphausen's troops crossed from Staten Island at midnight on June 6 and began landing at Elizabethtown Point. Almost immediately, things went wrong. One of the first shots fired severely wounded Brigadier General Thomas Stirling, throwing the 1st Division into confusion and costing the column precious hours. By sunrise, a force of just 60 New Jersey militiamen under Ensign Moses Ogden was fighting a rearguard action in an orchard near Governor Livingston's mansion. They were swept aside, but they had bought time. At about eight in the morning, Brigadier General William Maxwell and his New Jersey Brigade received the main British assault. Using trees and bushes for cover, the Americans held their ground for three hours until reinforcements swelled the British force to 3,000 men. Even then, as Knyphausen himself noted, the rebels 'withdrew from house to house and from wood path to wood path, resisting with all means available.' The British plundered the village and burned at least a dozen houses.

It was during this fighting that Hannah Caldwell was killed. The maid, Abigail Lennington, saw the soldier approach the window. Thomas Fleming's account describes the scene: a bright, sunny day, a nervous infantryman who could barely see into a room with windows on only one wall, and a movement - any movement - that was enough to make him fire. Moments later, the soldier's squad entered the house and began ransacking it before officers ordered them out. Hannah's death, and the burning of the village, became powerful propaganda for the Patriot cause. Her husband would go on to play a memorable role at the Battle of Springfield two weeks later, bringing hymn books to serve as artillery wadding and urging the gunners, 'Give 'em Watts, boys!' - a double meaning referencing the hymnist Isaac Watts. James Caldwell himself would be shot dead by an American sentry the following year.

That evening, Knyphausen took stock. He had failed to reach Hobart Gap. The numbers of militia who assembled to oppose him shocked his commanders - some had marched from as far away as Hopewell, over forty miles to the southwest. If he pressed forward, he faced a general engagement with Washington's entrenched army on high ground, with militia swarming his flanks. He decided to withdraw. The next day saw minor skirmishing as the British retraced their steps to Elizabethtown Point. Continental casualties for the day were 12 killed, 50 wounded, and 13 missing, though militia losses were not included in the official return. A fortnight later, Knyphausen tried again at the Battle of Springfield, with equally disappointing results. The combined British losses for both engagements were 25 killed, 234 wounded, and 48 missing.

Today, Union Township has long since absorbed the rural landscape where militiamen fought from behind trees and stone walls. Connecticut Farms Cemetery, on Stuyvesant Avenue, preserves the memory of the community that existed before the battle remade it. The Caldwell Parsonage, rebuilt in 1782 after the original was burned, still stands on Caldwell Avenue as a museum operated by the Union Township Historical Society. What makes this battle significant is not its scale but its consequence: Knyphausen's failure here and at Springfield two weeks later effectively ended British ambitions in New Jersey and demonstrated that the militia - often dismissed by professional soldiers on both sides - could fight with tenacity that altered the course of campaigns.