Washington's spies counted a British army onto its ships

The boats had been coming in on the shingle since the afternoon: flat-bottomed craft filling with men in scarlet coats and pulling out again to the transports lying at anchor where the East River widens into Long Island Sound. Loading an army takes hours, and this was a large one. Somewhere above the beach, on the wooded bluff or the road behind it, somebody was counting.

What he wrote reached Alexander Hamilton, Washington's aide, at the army's headquarters at Preakness on the afternoon of 21 July 1780: 8,000 troops are this day embarking at Whitestone. Hamilton wrote to Lafayette the same day that the enemy "are making an embarkation with which they menace the French fleet and army."

He was right about the destination. Eleven days earlier a French fleet had come into Newport: seven ships of the line and about six thousand soldiers under the Comte de Rochambeau, the first French army to land on the American mainland and fight alongside the Continentals. It arrived barely able to stand. Seventy days at sea had put fifteen hundred sailors and eight hundred soldiers ashore sick; the guns were not yet landed and the earthworks were not yet dug. Sir Henry Clinton, commanding the British in North America, heard of the arrival on 18 July — his navy had missed it for a week — and saw the opening at once. Break Rochambeau in his first fortnight and France might be out of the American war altogether.

Who was watching the British at Whitestone

Nobody knows, which is close to being the point of the organisation. The network is now called the Culper Ring: Washington set it up on British-occupied Long Island in August 1778 and it stopped writing in the summer of 1782, and 193 of its letters survive, 383 pages in all. Its members signed them with names that were not theirs. Benjamin Tallmadge, the dragoon major who ran it, was John Bolton. Abraham Woodhull, a farmer at Setauket, was Samuel Culper — Culper Senior once there was a Junior, and the Junior, the ring's man inside Manhattan, went unidentified for a hundred and fifty years.

Christian McBurney, who has reconstructed that fortnight day by day, credits the Whitestone report to him: Robert Townsend, a Quaker merchant from Oyster Bay whose family house had been requisitioned as a British regimental headquarters. In the occupied city he kept a dry-goods business, wrote a social column for a Loyalist newspaper and held a share in a coffee house with James Rivington, the king's printer. British officers talk in coffee houses. Hamilton himself said only that his news came "from New York through different channels" — the phrasing of a man protecting a source.

How Washington's spies got a message off Long Island

By road, then by water, then by road again, and slower at every stage than anyone involved would have liked. A report gathered in Manhattan went overland to Setauket — fifty-five miles, ridden for three years by a tavern keeper named Austin Roe, who made the trip often enough that his face stopped being interesting at the checkpoints. There it passed to Woodhull, who lived by his own account in more or less continuous fear, and on to Caleb Brewster, a whaleboat captain who rowed it across Long Island Sound to Connecticut. Tallmadge was waiting at the far end, and express riders carried it to headquarters.

The tradecraft itself was good. In July 1779 Tallmadge compiled a numbered codebook: a pocket dictionary of some seven hundred and ten words, each with its number. He was 721, Woodhull 722, Townsend 723, Washington 711, New York 727. Over the top of the numbers went an invisible ink, worked out by a physician named James Jay and brought to Washington in 1778 by his brother John, who ran secret correspondence for the Continental Congress. A letter would discuss the price of flour in ordinary ink, with the real message between the lines and invisible until a second chemical was brushed across the page.

How long a Culper letter took to reach Washington

Long enough to ruin it, often. The editors of the Washington Papers at Virginia have traced one letter in detail: Woodhull wrote it at Setauket on 16 August 1780, and Washington probably did not read it until 28 August. Twelve days, in which Admiral Arbuthnot's fleet had sailed and the intelligence had become worthless. Espionage in 1780 travelled at the speed of a horse and a rowing boat, and a spy could be entirely right and still be too late.

It was fragile in a more ordinary way too. Ten weeks before Whitestone the ring had, in effect, resigned: on 8 May 1780 Tallmadge reported flatly to Washington that "C. Senior grows timid, & thinks the intercourse had better be dropt for the present," enclosing a letter in which Culper Junior declined to continue at all and asked for a replacement in New York. Reports began arriving again anyway, which is why there was anybody at Whitestone that July to do the counting.

Did the Culper Ring save the French at Newport

No, and the claim is worth taking apart, because it is the one most often made for the ring. McBurney's reconstruction shows at least two warnings reaching Rhode Island ahead of the Culper report. Colonel Samuel Blachley Webb came in by sloop on the afternoon of 24 July with a written account of the embarkation; Colonel Henry Babcock's messenger arrived the same day with corroborating intelligence from Long Island. Hamilton's express rider did not reach Lafayette's quarters until just before midnight on the 25th, by which time Rochambeau had already pronounced his defences respectable.

What it did do was reach Washington early, on the 21st, and Washington used it. He prepared a movement against Kingsbridge, the narrow northern gateway onto Manhattan, on the calculation that a credible threat to New York City would keep Clinton's army at home. Whether that is what decided Clinton cannot be proved, and the honest version of this story does not claim it. The ending is not in doubt, though. By 28 July more than seventy transports lay at anchor in Huntington Bay with eight thousand men aboard in high summer, waiting for orders that never came. The expedition was abandoned and the men went ashore again; Newport was never attacked; and a year later the army that had sat in those transports watched Rochambeau march south past New York towards Yorktown.

Was Agent 355 a real person

There is no evidence that she existed. The whole legend of a beautiful woman spy inside the British command in New York rests on a single clause in a letter Woodhull wrote on 15 August 1779.

I intend to visit 727 before long and think by the assistance of a 355 of my acquaintance, shall be able to outwit them all.

Abraham Woodhull, writing as Samuel Culper, 15 August 1779

727 is New York. 355, in Tallmadge's codebook, is the number for the word lady. Woodhull was saying that he meant to go into the city, and that he knew a woman there who could help him. Everything else — the name, the romance, the capture, the death aboard the prison ship Jersey — was added later by people who wanted a better story: Morton Pennypacker in the 1930s, Brian Kilmeade's 2013 bestseller George Washington's Secret Six, and AMC's TURN, which dramatised the folklore rather than the letters and is very good television.

The other famous details go the same way. Bill Bleyer, who read all 193 surviving letters, reports that not one mentions Anna Strong's black petticoat on the clothesline — the signal that supposedly told Brewster which cove to use — and there is no documentary support for the buried box in Woodhull's pasture. James Rivington was almost certainly not a member: Townsend's ledgers show that he bought Rivington's newspaper, and the number 726 most likely stood for the paper rather than the man.

Was anyone in the Culper Ring ever caught

Not one of them, in seven years, in a city under military occupation. They stopped writing in July 1782 and went back to being farmers and shopkeepers. It is worth remembering what they were being so careful about. Four years before Whitestone, Washington had sent a young Connecticut officer into the same occupied city with no cover story, no cipher and his Yale diploma in his pocket. Nathan Hale was taken near Flushing Bay, a few miles along the shore from the beach where the boats would load in 1780, and hanged the next morning without trial. He was twenty-one, and he had been Benjamin Tallmadge's classmate at Yale.

Afterwards they mostly kept quiet. Caleb Brewster settled in Connecticut as a blacksmith and farmer, served for years as an officer in the United States Revenue Cutter Service and died at Black Rock in 1827, aged seventy-nine. Woodhull farmed, and later became a judge. Tallmadge became a congressman for Connecticut. Robert Townsend said nothing at all: he lived until 1838 and nobody who knew him ever learned what he had done. His identity was established only around 1930, when Pennypacker found a cache of his papers at Oyster Bay and had the handwriting matched against the Culper letters. A hundred and fifty years of cover, ended by a signature match.

On 25 November 1783 the last British troops left Manhattan and Washington rode back into the city he had spent seven years watching from outside it. Six years later he took the presidential oath at Federal Hall, a few streets from where Culper Junior had kept his shop. Whitestone is a quiet corner of northern Queens now, under the approach of a suspension bridge. The ground was once the estate of Francis Lewis, a signer of the Declaration whose house the British burned in 1776. There is a small park on the shore there now, named for him, looking out over the water where the transports lay.