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DIESKAU, JEAN-ARMAND (Johan Herman?), Baron de DIESKAU, army officer, governor of Brest, commander of the French regular troops in Canada; b. 1701, in Saxony; d. 1767, at Suresnes (dept. of Hauts-de-Seine), France.

Jean-Armand Dieskau, a Saxon in the French service, was the protégé of the Maréchal de Saxe, the finest general of French armies between Turenne and Napoleon. Dieskau was brought to France by his compatriot as an aide-de-camp in 1720 and served with him in various campaigns from 1733 to 1744. He became a colonel of cavalry, and apparently fought as such at Fontenoy (Belgium); in 1747 he was made major-general and military governor of Brest, the chief French naval base on the Atlantic.

On 1 March 1755 he was appointed commander of the battalions of French regulars being sent as reinforcements to Canada, and arrived in Quebec in June on the Entreprenant. His authority, while great, was scarcely absolute, for his instructions specifically made him subordinate to Governor General Pierre de Rigaud* de Vaudreuil. Baron Dieskau’s role, therefore, was that of a battlefield commander with control of tactics but not of strategy.

By the summer of 1755, largely through the capture of Edward Braddock’s papers at the battle of the Monongahela in July, the French knew of British plans for an attack on Fort Frontenac (Kingston, Ont.) and Fort Niagara (near Youngstown, N.Y.) as well as on Fort Saint-Frédéric (Crown Point, N.Y.) on Lake Champlain. Vaudreuil considered the former operation a greater danger and planned a countermove against Oswego to deprive the British of their base of operations on the Great Lakes. Dieskau was to direct it with a force of some 4,000 men.

While his force was assembling at Fort Frontenac, reports came in from Lake Champlain that the British expedition against Saint-Frédéric, commanded by Colonel William Johnson*, was already under way, threatening to ravage the country up to Montreal. Dieskau was called back by August 1755 and sent down the Richelieu against Johnson’s colonial militia, now at the head of Lac Saint-Sacrement (Lake George). The French were encamped on the future site of Fort Carillon (Ticonderoga, N.Y.) by 1 September. Some of Dieskau’s soldiers had been left at Fort Frontenac, so that his force was now smaller: 1,500 regulars, 1,000 militia, five to six hundred Indians. Johnson could muster some 3,000 colonial militia and 300 Indians, mostly Mohawks commanded by their chief Theyanoguin.

When word of the French arrival at the Ticonderoga site reached Johnson, he decided to build a fort at the head of Lake George, at the site of the future Fort William Henry (also called Fort George, now Lake George, N.Y.), 14 miles northwest of his first base, Fort Edward, on the Hudson River. Dieskau became aware of this division of enemy forces on 3 September through a prisoner. But he was led to believe that the British army had retired to Albany, leaving only 500 men at Fort Edward, and that Johnson’s expected reinforcements – some 2,400 militia – would ignore this fort on their way to Lake George.

Dieskau saw in this news a marvellous opportunity to destroy the 500 colonials at Fort Edward and thus cut off the rest of Johnson’s army at Lake George. This strategy would have been sound, if his intelligence had been accurate and he had moved with all his men. But he divided his forces and set off for Fort Edward with an élite corps of 1,500 men: some 200 regulars, 600 militia, and about 700 Indians including 300 Mohawks from Sault-Saint-Louis (Caughnawaga, Que.). He left behind at Ticonderoga 1,300 regulars and 400 militia as defence against any British attack. In dividing his strength, he not only disobeyed orders, but displayed a fatal overconfidence against mere colonials.

By 7 September his detachment had reached the Hudson River. At this point, however, the Indians refused to attack Fort Edward. Had Dieskau been more familiar with Indian warfare, he could have predicted their reluctance to assault fortified positions equipped with cannon. At the prospect of attacking with drastically reduced forces, Dieskau chose to divert his attack to the head of Lake George where the enemy were less solidly entrenched and had fewer cannon. The Indians agreed to support him.

On 8 September, he led his regulars along the wagon road to Lake George, with Indians and militia flanking them on the difficult terrain. On this march the French became aware that Johnson was sending 1,000 men to relieve Fort Edward, which he assumed was under attack. Dieskau laid plans for an ambush; he posted his disciplined regulars in formation on the road, his Indians and militia in advance on both forest flanks with instructions to hold their fire until the regulars fired. Into a similar trap Braddock had fallen. Success depended upon both militia and Indians keeping silent until the last moment. Whether by accident or because the Indians wished to warn their Mohawk cousins – Dieskau, of course, believed the latter – the trap was sprung prematurely. Both Colonel Ephraim Williams and Theyanoguin were killed, but their troops were able to retreat though in confusion.

Dieskau’s pursuit of the terrified mob was hampered by the near exhaustion of his Indians and militia. Thus only his 200 regulars reached the British camp at Lake George on the heels of the defeated detachment. Johnson had fortified his position with anything available – carts, tree trunks, overturned boats – and had mounted cannon. Dieskau was confronted with the classic military problem of frontal assault on a prepared position. His regulars, with parade ground precision, marched to the assault; the militia, when they caught up, fired on the British from the flanks, as did some Indians. After several hours the battle ended in a stalemate. Dieskau himself was wounded three times in the legs and propped against a tree by his second in command, Pierre-André de Montreuil*. Even when the French finally retreated, Dieskau refused to be moved, allegedly stating he might as well die there as in bed. Later a British soldier (according to Dieskau a renegade Frenchman) shot him through the groin.

The British colonials claimed a major victory, not merely a tactical one. It was, in fact, a strategic stalemate: the British remained at what became Fort William Henry; the French constructed Fort Carillon. The British thrust of 1755 was stopped, and the French would capture William Henry before the final British victory.

Baron Dieskau survived his wounds. He was taken to New York, then to London, and then for treatment of his still unhealed wound in the groin to Bath, whence he dispatched letters to the French government, outlining his medical condition in graphic detail, emphasizing his lack of funds, and justifying his conduct, usually in that order. With peace in 1763, he was repatriated to France.

Contemporaries were, on the whole, condemnatory. Vaudreuil was vehement: Dieskau, by contravening orders not to divide his forces, had lost a chance to “massacre” the British. Montreuil, anxious to refute any accusation of abandoning his chief on the battlefield, was almost equally accusatory. André Doreil, the war commissary, noted that Dieskau was too rash for top command. But Dieskau had gambled, and lost. Aware that French regulars in Canada could not easily be replaced, he decided, understandably, to risk only 200 of them on a wilderness march. He showed adaptability to North American warfare in his attempt at ambush and also personal bravery at Lake George. With accurate intelligence, his actions might well have proved successful; at the least he stopped an invasion, and inflicted casualties as severe as those he received.

J. R. Turnbull

[Primary sources for a biography of Dieskau are fairly extensive: AN, Col., B, C^11A and F³, all contain material. His “dossier personnel” in AN, Col., E, 134, is also useful, as is material in the SHA. The “Lettres de Doreil,” APQ Rapport, 1944–45, contains an assessment of Dieskau, and the Johnson papers (Sullivan et al.) also includes material. The NYCD (O’Callaghan and Fernow), X, gives a full account in English of the French records, including the famous dialogue between Dieskau and the Maréchal de Saxe – an apologia for Dieskau’s conduct of the battle. Secondary sources that give more than cursory mention are reasonably numerous. Gipson, British empire before the American revolution, VI, throws light on British strategy and makes good use of the Johnson papers. Frégault, Canada: the war of the conquest, is indispensable for the French side. I. K. Steele, Guerillas and grenadiers, the struggle for Canada, 1689–1760 (Frontenac Library, 3, Toronto, 1969), briefly but succinctly sums up the military situation, and Stanley, New France, provides a somewhat fuller treatment.  j.r.t.]