Battles are complicated events where conflicting or unclear information can confuse even good generals. Here are some examples of when American intelligence systems failed, usually with terribly tragic results.
In late 1775 the Continental Congress planned to neutralize threats from Canada by seizing Montreal. Gen. George Washington, commanding the Continental Army at Boston, decided to support the effort by sending a force north from Boston through the Maine wilderness to seize Quebec. It seemed like a good idea at the time. Washington expected light resistance at Quebec and an easy passage through the highlands of Maine by way of the Kennebec and Dead Rivers. “I made all possible inquiry as to the distance, the safety of the route and the danger of the season,” he wrote, “but found nothing in either to deter me from proceeding.” He chose the rising star Col. Benedict Arnold to command the expedition.
Washington was way off. He gained much of his knowledge about the northern frontier from a 1761 map by a British Army engineer and underestimated the ruggedness of the terrain. Arnold’s expedition departed in September and endured an exceptionally harsh passage through the Maine highlands that destroyed their supplies, bled off their numbers, and exhausted the soldiers. Arnold wrote to Washington during the trek, “I have been much deceived in every account of our route, which is longer and has been attended with a thousand difficulties I never apprehended.” Slowed by the difficult northward trudge, the expedition did not arrive outside Quebec until December 13. Then they faced British reinforcements that arrived only days before them. Arnold wrote Washington, “had I been ten days sooner Quebec must inevitably have fallen into our hands, as there was not a man there to oppose us.” Their second adversary, the brutal Canadian winter, also arrived.
A week later the other half of the American invasion force, Brig. Gen. Richard Montgomery’s troops from Montreal, joined Arnold. The combined force attacked Quebec in a snowstorm in the early morning hours of December 31. The assault failed at the cost of 200 American lives. Montgomery was among the dead and Arnold severely wounded.
Had the Americans applied their intelligence more effectively, they could have avoided, or at least better handled, this dramatic but disaster-prone expedition.
In August 1776, 15,000 British troops under Gen. William Howe landed on Long Island, threatening New York City. In between them and Manhattan stood a fortified American defensive line south of Brooklyn.
Incorporating a rugged ridge known as the Gowanus Heights, the American line was a solid defense. But at that early stage of the war the Continentals lacked both a spy network on Long Island and an effective cavalry force. The result was that neither Gen. Washington nor Maj. Gen. Israel Putnam, the commander of the defenses, fully understood the battlefield or British intentions and movements. The Americans heavily defended and fortified three natural passes that formed avenues through the Heights; the Martense Lane Pass, Flatbush Pass, and Bedford Pass. But the Jamaica Pass, at the east end of the line, went unfortified. Only two battalions of riflemen under Col. Samuel Miles had orders to watch the area and report any enemy movement. The commander of the left of the American line, Maj. Gen. John Sullivan, also posted a patrol of five mounted officers to observe the Jamaica Road which ran through the pass. Sullivan later wrote that he was “very uneasy” about the road, “through which I had often foretold the enemy would come, but could not persuade others to be of my opinion.”
Sullivan’s concern was valid. Howe’s British troops thoroughly scouted the area and gained information from local Loyalists. His subordinate, Gen. Henry Clinton, also knew the area from time he spent there in his youth. “I took some pains to reconnoiter” Clinton wrote, which led him to realize that the Jamaica Pass offered an avenue to maneuver behind the Continental defenses. Clinton suggested to Howe a British attack through the pass to turn the American flank.
Howe detested Clinton, but grudgingly agreed with the plan. On the night of August 26, Clinton marched east to Jamaica Pass with about 10,000 troops, two-thirds of the British force. They moved, unnoticed, within two miles of a brigade of New York militia under Brig. Gen. Nathaniel Woodhull. At Jamaica Pass, Gen. Sullivan and Col. Miles perceived signs of the enemy advance but whether they properly warned their senior commanders is unclear. That night Clinton’s troops captured Sullivan’s mounted patrol and learned that Jamaica Pass was essentially unguarded.
The next morning, British and Hessian troops pinned down the Americans at the Martense Lane and Flatbush Passes. At about the same time Clinton and Howe personally led their main force through Jamaica Pass to overwhelm the American left flank. Putnam’s defensive line crumbled and the troops retreated to Brooklyn.
Washington took personal command of the Long Island defenses but with his forces outnumbered and outflanked the situation was hopeless. On August 29 Washington evacuated his forces to Manhattan, which relinquished Long Island to the Crown for the rest of the war.
In July 1777, Gen. Howe’s army departed New Jersey by sea in a naval convoy of over 200 ships. Washington had little intelligence on its destination, and for weeks he thought that Howe was headed for the Hudson River, Philadelphia, or South Carolina. Howe’s landing at the north end of the Chesapeake Bay at the end of August pointed to Philadelphia as Howe’s target.
Washington chose to defend Philadelphia on the banks of Brandywine Creek, southwest of the city. The American defense adequately covered five fords across the creek, and Washington was wary of an enemy crossing on his open right flank. There, he posted Maj. Gen. John Sullivan and cavalry under Col. Theodorick Bland to cover three more fords and the vulnerable flank. But the American reconnaissance was, again, incomplete. Two miles to the west, beyond where Sullivan and Bland watched, two more fords crossed the Brandywine. Just as at Long Island, Howe found the fords thanks to thorough scouting and a local Loyalist. Much like Jamaica Pass, Howe knew that the open crossing offered an avenue to turn the American right flank.
The battle of Brandywine nearly repeated the battle of Brooklyn. On September 11 Howe launched a diversionary attack on the American front. At the same time Howe and Gen. Charles Cornwallis led a larger force to the northwest, crossed the Brandywine at the unguarded fords, and crashed onto the American right flank. Washington received so many confusing reports of the action that he later told Congress, “the intelligence received of the enemy’s advancing up the Brandywine, and crossing at a ford about six miles above us, was uncertain and contradictory.” The Americans repositioned their line and fought stubbornly, but could not halt the British attack.
Washington withdrew his army east to the town of Chester and two weeks later Howe’s army marched into Philadelphia.
Gen. Horatio Gates, the famed victor of Saratoga, took command of the Continental Army’s Southern Department at a camp at Hollinsworth’s Farm on the Deep River in North Carolina on July 25, 1780, already armed with intelligence. The bulk of the British and Loyalist army under Lord Charles Cornwallis was at Charleston, South Carolina. According to Gen. Thomas Sumter of the South Carolina militia, Lord Francis Rawdon held an exposed post at the town of Camden, South Carolina with only 700 Loyalist troops. Gates decided to march to Camden and sweep away Rawdon’s outpost, and his army departed on July 27.
Gates was making a series of intelligence mistakes. To begin with, he failed to understand his area of operation. His senior commanders suggested somewhat circuitous routes to Camden where the army could sustain itself, but Gates chose a route that was direct but heavy in Loyalist sentiment and barren of forage. This forced the Americans to consume meager rations of green corn, peaches and thin soup that some officers thickened with wig powder. Gate’s second error was that he moved with a cavalry force that was too small to adequately scout ahead and keep track of enemy dispositions. “Fatal mistake!” observed the veteran cavalryman Lt. Col. Henry Lee. The Americans closed on Camden on August 15 unaware that Cornwallis’s army was not in Charleston, but actually concentrated at Camden.
It was on August 9 that Cornwallis, who “was regularly acquainted by Lord Rawdon with every material incident or movement” the Americans made, as he later wrote, learned that Gates was headed toward Camden. Marching from Charleston, Cornwallis’s army arrived at Camden two days before Gates. Continental and Loyalist cavalry patrols clashed the night of August 15, revealing the presence of Cornwallis’s force. Gates’s adjutant, Col. Otho Holland Williams, recalled that when Gates learned that he faced Cornwallis’s entire army, “the general’s astonishment could not be concealed.” Gates called a council of war and asked his senior commanders, “Gentlemen, what is best to be done?”
The Council agreed that they had no choice but to fight Cornwallis the next day, and with that, Gates’s subordinate commanders began sharing the intelligence mistakes. With roughly 3,000 soldiers the Americans outnumbered the British by about 800 men. Gates formed his line of battle in the early morning of August 16, but made the mistake of posting his most inexperienced soldiers, the North Carolina and Virginia militia, on the left of his line where they would oppose the most senior and experienced British brigade. As a former king’s officer Gates should have known that by tradition, British commanders routinely assigned their most senior units to the right side of their battle lines. He also should have realized the advantage that gave the British against the militia he expected to fight them. The reasons for Gates’s decision, and the extent that the subordinate American commanders accepted or disagreed with the assignment, is open to debate. Either way, the decision rebalanced the odds in Cornwallis’s favor.
Gates opened the battle by advancing the militia on the left of his line but Cornwallis immediately counterattacked against the move. The advance of the veteran British regulars set the American militia to flight. The American line crumbled and the cavalry of Lt. Col. Banastre Tarleton’s British Legion swept in and completed the rout. American losses were probably 250 killed and 800 wounded, many of whom were captured, compared to 68 killed and 256 wounded in Cornwallis’s army. The loss at Camden was an absolute disaster and a major blow to American cause in the South.
This is only a partial list of how commanders employed and interpreted their intelligence. Please feel free to share other examples with your comments.
 Robert McConnell Hatch, Thrust for Canada: The American Attempt on Quebec in 1775-1776 (Boston; Houghton Mifflin, 1979), 62.
 Arnold to Washington, October 27 1775, George Washington Papers at the Library of Congress, accessed January 5, 2015, http://memory.loc.gov/cgi-bin/ampage?collId=mgw4&fileName=gwpage034.db&recNum=605.
 Arnold to Washington, November 20 1775, George Washington Papers at the Library of Congress, accessed January 5 2015, http://memory.loc.gov/cgi-bin/ampage?collId=mgw4&fileName=gwpage034.db&recNum=890.
 Sullivan, letter dated October 25, 1777, in The Bulletin of the Historical Society of Pennsylvania, Vol. I, 1845-1847 (Philadelphia, Merrihew & Thompson, 1848), “Papers Relating to the Battle of Brandywine,” 52. Sullivan’s letter could have been self-serving – he wrote it a year after the battle as part of his defense of his actions at the battle of Brandywine.
 Sir Henry Clinton, The American Rebellion: Sir Henry Clinton’s Narrative of His Campaigns, 1775 – 1782, with an Appendix of Original Documents, William B. Willcox, ed., (New Haven: Yale University Press, 1954), 41.
 See Barnet Schecter, The Battle for New York: The City at the Heart of the American Revolution (New York: Walker & Company, 2002), 133-135.
 Washington to The President of Congress, at Midnight, Chester, September 11, 1777, Writings of George Washington, Vol. 9, accessed February 11, 2015, http://etext.virginia.edu/washington/fitzpatrick/. Adjutant General Pickering actually wrote this dispatch at Washington’s direction.
 Henry Lee, The Revolutionary Memoirs of General Henry Lee, Edited with a Biography of the Author by Robert E. Lee (1812, reprint, New York: DeCapo Press, 1998), 172. Lee was not assigned to the Southern Department in August 1780, but I consider his professional observation valid.
 Charles, Earl Cornwallis to Lord George Germain, August 21 1780, State Records of North Carolina XV: 269-273, accessed February 11, 2015, http://www.battleofcamden.org/cornwallis2germain_txt.htm.
 Otho Holland Williams, A Narrative of the Campaign of 1780, (A. E. Miller, Charleston, South Carolina, 1822), accessed February 15, 2015, “Documentary History of the Battle of Camden, 16 August 1780,” http://battleofcamden.org/.
 For a thorough assessment of how Gates and the entire Southern Department performed at this battle, see “Unlucky or Inept? Gates at Camden,” by Wayne Lynch, https://allthingsliberty.com/2014/05/unlucky-or-inept-gates-at-camden/.