For several months the Allies had been planning an attack on Brest, the French port in the West of Brittany. The French had received intelligence alerting them to the imminent assault, enabling Marshal Vauban to strengthen its defences and reinforce the garrison. Inevitably the attack on 18 June led by Thomas Tollemache ended in disaster; most of his men were killed or captured, and Tollemache died of his wounds shortly afterward. Despite lacking evidence, Marlborough's detractors claimed that it was he who had alerted the enemy. Macaulay states that in a letter on 3 May 1694 Marlborough betrayed the Allied plans to James, thus ensuring that the landing failed and that Tollemache, a talented rival, was killed or discredited as a direct result. Historians such as John Paget and C. T. Atkinson conclude that he probably did write the letter, but did so only when he knew that it would be received too late for its information to be of any practical use (the plan of the attack on Brest was widely known, and the French had already begun to strengthen their defences in April). To Richard Holmes, the evidence linking Marlborough with the Camaret Bay letter (which no longer exists), is slender, concluding, "It is very hard to imagine a man as careful as Marlborough, only recently freed from suspicion of treason, writing a letter which would kill him if it fell into the wrong hands". However, David Chandler surmises that "the whole episode is so obscure and inconclusive that it is still not possible to make a definite ruling".
For several months the Allies had been planning an attack on Brest, the French port in the West of Brittany. The French had received intelligence alerting them to the imminent assault, enabling Marshal Vauban to strengthen its defences and reinforce the garrison Inevitably the attack on 18 June led by Thomas Tollemache ended in disaster; most of his men were killed or captured, and Tollemache died of his wounds shortly afterward. Despite lacking evidence, Marlborough's detractors claimed that it was he who had alerted the enemy. Macaulay states that in a letter on 3 May 1694 Marlborough betrayed the Allied plans to James thus ensuring that the landing failed and that Tollemache, a talented rival, was killed or discredited as a direct result. Historians such as John Paget and C. T. Atkinson conclude that he probably did write the letter, but did so only when he knew that it would be received too late for its information to be of any practical use (the plan of the attack on Brest was widely known, and the French had already begun to strengthen their defences in April). To Richard Holmes, the evidence linking Marlborough with the Camaret Bay letter (which no longer exists), is slender, concluding, "It is very hard to imagine a man as careful as Marlborough, only recently freed from suspicion of treason, writing a letter which would kill him if it fell into the wrong hands". However, David Chandler surmises that "the whole episode is so obscure and inconclusive that it is still not possible to make a definite ruling".