After his victories over Washington at Brandywine and Paoli, Gen Howe felt that he had the opportunity to open Philadelphia to the sea. So he sent Hessian detachments to reduce the American forts on the Delaware River, while the bulk of his army camped at Germantown, Pennsylvania.
But the Continental Army wasn’t defeated. Mistakes were made at Brandywine and Paoli, but they were due more to the relative lack of professionalism in the Army, than in any collapse in morale. The Continental Army had fought well at Brandywine, and was still full of fight. Washington planned to make Howe pay for the arrogance of splitting his army. Washington decided to recreate the Battle of Trenton from the previous Christmas: He’d surprise Howe at Germantown in a dawn attack. But instead of crossing the Delaware River in secrecy, he’d march four separate columns through the exceptionally dark and foggy autumn night. Then he’d have all four columns converge on Howe precisely as the sun broke the horizon. Howe would never expect it.
Washington did surprise Howe, but of the four columns, only two arrived, and neither at the same time. The plan was for Sullivan and Greene to attack the center, as two columns of militia attacked the flanks of the British camp. The militia columns never arrived, one got lost and the other was held up by a small Hessian outpost. In the foggy morning, Sullivan arrived on time, but Greene was delayed and began his attack later than Sullivan, whom he still didn’t have contact with. Both columns pushed the British light infantry, who fought savagely to give the line regiments time to organize. Sullivan’s advanced guard almost captured an incredulous Howe and his staff, who rode forward to admonish the light infantry for running from “skirmishers and foraging parties”.
Washington’s plan further broke down when the 40th Regiment of Foot barricaded itself in Clivden, the name for the stout stone mansion of the chief justice of the Pennsylvania Judiciary, John Chew. Sullivan wisely left a regiment to contain the British in Clivden, and bypassed to continue the assault. However, Henry Knox and the reserve arrived, and he convinced Washington to let him reduce the house with his guns. While Knox was setting up his cannon, one of Greene’s brigades, who was lost, stumbled into one of Sullivan’s brigades in the fog. They mistook each other for redcoats and opened fire. Both brigades broke.
At Clivden, Knox poured fire from his light guns into the mansion, which proved amazingly resilient. Unfortunately, Sullivan’s men, who were so far successful, heard Knox’s cannon behind them, and assumed they were out maneuvered just as they had been at Brandywine. Furthermore, their officers were coming to the realization that the militia attacks on the flanks had not materialized and Greene’s men were nowhere to be found (They were at least fighting though, just not where Sullivan expected them to be). Sullivan’s two remaining brigades felt they were out maneuvered, outnumbered, and alone. They too broke and ran.
Howe never expected a dawn surprise assault by the Washington because the bold plan was beyond the capabilities of his army, much less the Continental Army. Nonetheless it was the best chance Washington had to seize the initiative and defeat Howe before setting into winter quarters. If it would have worked, we’d be talking about Germantown instead of Saratoga as one of the decisive battles of the American Revolution. But it was not to be.