philadelphia. howe outmaneuvered washington at the battle of brandywine on september 11, 1777, and marched unopposed into the nation's capital at philadelphia. a patriot attack failed against the british at germantown in october. major general thomas conway prompted some members of congress (referred to as the conway cabal) to consider removing washington from command because of the losses incurred at philadelphia. washington's supporters resisted, and the matter was finally dropped after much deliberation. once the plot was exposed, conway wrote an apology to washington, resigned, and returned to france. washington was concerned with howe's movements during the saratoga campaign to the north, and he was also aware that burgoyne was moving south toward saratoga from quebec. washington took some risks to support gates' army, sending reinforcements north with generals benedict arnold, his most aggressive field commander, and benjamin lincoln. on october 7, 1777, burgoyne tried to take bemis heights but was isolated from support by howe. he was forced to retreat to saratoga and ultimately surrendered after the battles of saratoga. as washington suspected, gates' victory emboldened his critics. biographer john alden maintains, "it was inevitable that the defeats of washington's forces and the concurrent victory of the forces in upper new york should be compared." the admiration for washington was waning, including little credit from john adams. british commander howe resigned in may 1778, left america forever, and was replaced by sir henry clinton. valley forge and monmouth washington and lafayette at valley forge by john ward dunsmore (1907), depicting washington and marquis de lafayette at valley forge washington rallying the troops at monmouth by emanuel leutze (1851–1854), depicting washington at the battle of monmouth in new jersey in june 1778 washington's army of 11,000 went into winter quarters at valley forge north of philadelphia in december 1777. they suffered between 2,000 and 3,000 deaths in the extreme cold over six months, mostly from disease and lack of food, clothing, and shelter. meanwhile, the british were comfortably quartered in philadelphia, paying for supplies in pounds sterling, while washington struggled with a devalued american paper currency. the woodlands were soon exhausted of game, and by february, lowered morale and increased desertions ensued. washington made repeated petitions to the continental congress for provisions. he received a congressional delegation to check the army's conditions and expressed the urgency of the situation, proclaiming: "something must be done. important alterations must be made." he recommended that congress expedite supplies, and congress agreed to strengthen and fund the army's supply lines by reorganizing the commissary department. by late february, supplies began arriving. baron friedrich wilhelm von steuben's incessant drilling soon transformed washington's recruits into a disciplined fighting force, and the revitalized army emerged from valley forge early the following year. washington promoted von steuben to major general and made him chief of staff. in early 1778, the french responded to burgoyne's defeat and entered into a treaty of alliance with the americans. the continental congress ratified the treaty in may, which amounted to a french declaration of war against britain. the british evacuated philadelphia for new york that june and washington summoned a war council of american and french generals. he chose a partial attack on the retreating british at the battle of monmouth; the british were commanded by howe's successor general henry clinton. generals charles lee and lafayette moved with 4,000 men, without washington's knowledge, and bungled their first attack on june 28. washington relieved lee and achieved a draw after an expansive battle. at nightfall, the british continued their retreat to new york, and washington moved his army outside the city. monmouth was washington's last battle in the north; he valued the safety of his army more than towns with little value to the british. west point espionage an 1800 engraving of washington made after his tenure commanding the continental army washington became america's first spymaster by designing an espionage system against the british. in 1778, major benjamin tallmadge formed the culper ring at washington's direction to covertly collect information about the british in new york. washington had disregarded incidents of disloyalty by benedict arnold, who had distinguished himself in many battles. in 1780, arnold began supplying british spymaster john andré with sensitive information intended to compromise washington and capture west point, a key american defensive position on the hudson river. historians have noted as possible reasons for arnold's defection to be his anger at losing promotions to junior officers, or repeated slights from congress. he was also deeply in debt, profiteering from the war, and disappointed by washington's lack of support during his eventual court-martial. arnold repeatedly asked for command of west point, and washington finally agreed in august. arnold met andré on september 21, giving him plans to take over the garrison. militia forces captured andré and discovered the plans, but arnold escaped to new york. washington recalled the commanders positioned under arnold at key points around the fort to prevent any complicity, but he did not suspect arnold's wife peggy. washington assumed personal command at west point and reorganized its defenses. andré's trial for espionage ended in a death sentence, and washington offered to return him to the british in exchange for arnold, but clinton refused. andré was hanged on october 2, 1780, despite his last request being to face a firing squad, to deter other spies. southern theater and yorktown king louis xvi of france aligned with washington and american patriots in support of the american revolution. generals washington and rochambeau give final orders before launching the siege of yorktown in yorktown, virginia in september 1781. in late 1778, general clinton shipped 3,000 troops from new york to georgia and launched a southern invasion against savannah, reinforced by 2,000 british and loyalist troops. they repelled an attack by american patriots and french naval forces, which bolstered the british war effort. in june 1778, iroquois warriors joined with loyalist rangers led by walter butler and killed more than 200 frontiersmen in june, laying waste to the wyoming valley in northeastern pennsylvania. in mid-1779, in response to this and other attacks on new england towns, washington ordered general john sullivan to lead an expedition to force the iroquois out of new york by effecting "the total destruction and devastation" of their villages and by taking their women and children hostage. the expedition systematically destroyed iroquois villages and food stocks, and forced at least 5,036 iroquois to flee to british canada. the campaign directly killed a few hundred iroquois, but according to anthropologist anthony f. c. wallace, the net effect of the campaign was to reduce the iroquois by half, who became unable to support themselves or survive the harsh winter of 1779–1780. rhiannon koehler estimates that as many as 5,500 iroquois, around 55.5% of the population, may have perished as a result of the campaign, which some historians have described as genocidal. washington's troops went into quarters at morristown, new jersey during the winter of 1779–1780 and suffered their worst winter of the war, with temperatures well below freezing. new york harbor was frozen, snow and ice covered the ground for weeks, and the troops again lacked provisions. clinton assembled 12,500 troops and attacked charlestown, south carolina in january 1780, defeating general benjamin lincoln who had only 5,100 continental troops. the british went on to occupy the south carolina piedmont in june, with no patriot resistance. clinton returned to new york and left 8,000 troops commanded by general charles cornwallis. congress replaced lincoln with horatio gates; he failed in south carolina and was replaced by washington's choice of nathaniel greene, but the british already had the south in their grasp. washington was reinvigorated, however, when lafayette returned from france with more ships, men, and supplies, and 5,000 veteran french troops led by marshal rochambeau arrived at newport, rhode island in july 1780. french naval forces then landed, led by admiral grasse, and washington encouraged rochambeau to move his fleet south to launch a joint land and naval attack on arnold's troops. washington's army went into winter quarters at new windsor, new york in december 1780, and washington urged congress and state officials to expedite provisions in hopes that the army would not "continue to struggle under the same difficulties they have hitherto endured". on march 1, 1781, congress ratified the articles of confederation, but the government that took effect on march 2 did not have the power to levy taxes, and it loosely held the states together. general clinton sent benedict arnold, now a british brigadier general with 1,700 troops, to virginia to capture portsmouth and conduct raids on patriot forces from there; washington responded by sending lafayette south to counter arnold's efforts. washington initially hoped to bring the fight to new york, drawing off british forces from virginia and ending the war there, but rochambeau advised grasse that cornwallis in virginia was the better target. grasse's fleet arrived off the virginia coast, and washington saw the advantage. he made a feint towards clinton in new york, then headed south to virginia. the siege of yorktown was a decisive allied victory by the combined forces of the continental army commanded by general washington, the french army commanded by the general comte de rochambeau, and the french navy commanded by admiral de grasse, in the defeat of cornwallis' british forces. on august 19, the march to yorktown led by washington and rochambeau began, which is known now as the "celebrated march". washington was in command of an army of 7,800 frenchmen, 3,100 militia, and 8,000 continentals. not well experienced in siege warfare, washington often referred to the judgment of general rochambeau and used his advice about how to proceed; however, rochambeau never challenged washington's authority as the battle's commanding officer. by late september, patriot-french forces surrounded yorktown, trapped the british army, and prevented british reinforcements from clinton in the north, while the french navy emerged victorious at the battle of the chesapeake. the final american offensive was begun with a shot fired by washington. the siege ended with a british surrender on october 19, 1781; over 7,000 british soldiers were made prisoners of war, in the last major land battle of the american revolutionary war. washington negotiated the terms of surrender for two days, and the official signing ceremony took place on october 19; cornwallis claimed illness and was absent, sending general charles o'hara as his proxy. as a gesture of goodwill, washington held a dinner for the american, french, and british generals, all of whom fraternized on friendly terms and identified with one another as members of the same professional military caste. asgill affair after the surrender at yorktown, a situation developed that threatened relations between the newly independent america and britain. following a series of retributive executions between patriots and loyalists, washington, in may 1782, wrote in a letter to general moses hazen that a british captain should be executed in retaliation for the execution of joshua huddy, a patriot captain, who was hanged at the direction of the loyalist richard lippincott. washington initially had wanted lippincott himself to be executed but was rebuffed. later that same month, charles asgill was chosen from amongst 13 british captains by the drawing of lots from a hat. this was a violation of the 14th article of the yorktown articles of capitulation, which protected prisoners of war from acts of retaliation. washington's feelings on matters soon changed, declaring in a june letter to general elias dayton, "i most devoutly wish his life may be saved." nonetheless, washington refused to reconsider the death sentence. rather, he passed on the responsibility of determining asgill's fate to the continental congress. after much consideration, and due in large measure to appeals from french foreign minister, the comte de vergennes, asgill was released to return to england in november 1782. peter henriques writes that the asgill affair "could have left an ugly blot on george washington's reputation", calling it "a blip that reminds us even the greatest of men make mistakes". demobilization and resignation general george washington resigning his commission by john trumbull (1824), a portrait that now hangs in the united states capitol rotunda when peace negotiations began in april 1782, both the british and french began gradually evacuating their forces. the american treasury was empty, unpaid, and mutinous soldiers forced the adjournment of congress,