About two weeks later, with forty men, Mosby raided a post at Herndon Station, bringing off a major, a captain, two lieutenants and twenty-one men, with a horse apiece. A week later, with fifty-odd men, he cut up about three times his strength of Union cavalry at Chantilly. Having surprised a small party, he had driven them into a much larger force, and the hunted had turned to hunt the hunters. Fighting a delaying action with a few men while the bulk of his force fell back on an old roadblock of felled trees dating from the second Manassas campaign, he held off the enemy until he was sure his ambuscade was set, then, by feigning headlong flight, led them into a trap and chased the survivors for five or six miles. Wyndham and Stoughton had found Mosby an annoying nuisance; their successors were finding him a serious menace. This attitude was not confined to the local level, but extended all the way to the top echelons. The word passed down, "Get Mosby!" and it was understood that the officer responsible for his elimination would find his military career made for him. One of the Union officers who saw visions of rapid advancement over the wreckage of Mosby's Rangers was a captain of the First Vermont, Josiah Flint by name. He was soon to have a chance at it. On March 31, Mosby's Rangers met at Middleburg and moved across the mountain to Chantilly, expecting to take a strong outpost which had been located there. On arriving, they found the campsite deserted. The post had been pulled back closer to Fairfax after the fight of four days before. Mosby decided to move up to the Potomac and attack a Union force on the other side of Dranesville--Captain Josiah Flint's Vermonters. They passed the night at John Miskel's farm, near Chantilly. The following morning, April 1, at about daybreak, Mosby was wakened by one of his men who had been sleeping in the barn. This man, having gone outside, had observed a small party of Union troops on the Maryland side of the river who were making semaphore signals to somebody on the Virginia side. Mosby ordered everybody to turn out as quickly as possible and went out to watch the signalmen with his field glasses. While he was watching, Dick Moran, a Mosby man who had billeted with friends down the road, arrived at a breakneck gallop from across the fields, shouting: "Mount your horses! The Yankees are coming!" It appeared that he had been wakened, shortly before, by the noise of a column of cavalry on the road in front of the house where he had been sleeping, and had seen a strong force of Union cavalry on the march in the direction of Broad Run and the Miskel farm. Waiting until they had passed, he had gotten his horse and circled at a gallop through the woods, reaching the farm just ahead of them. It later developed that a woman of the neighborhood, whose head had been turned by the attentions of Union officers, had betrayed Mosby to Flint.