This last would entail something of a sacrifice, for he had come to esteem Sir Percy highly as an opponent whose mind was an open book and whose every move could be predicted in advance. With Wyndham eliminated, he would have to go to the trouble of learning the mental processes of his successor. However, Wyndham would be the ideal captive to grace a Mosby triumph, and a successful raid on Fairfax Courthouse, garrisoned as it was by between five and ten thousand Union troops, would not only secure Mosby's position in his own army but would start just the sort of a panic which would result in demands that the Union rear be re-enforced at the expense of the front. So, on Sunday, March 8, Mosby led thirty-nine men through the gap at Aldie, the largest force that had followed him to date. It was the sort of a foul night that he liked for raiding, with a drizzling rain falling upon melting snow. It was pitch dark before they found the road between Centreville and Fairfax, along which a telegraph line had been strung to connect the main cavalry camp with General Stoughton's headquarters. Mosby sent one of his men, Harry Hatcher, up a pole to cut the wire. They cut another telegraph line at Fairfax Station and left the road, moving through the woods toward Fairfax Courthouse. At this time, only Mosby and Yank Ames knew the purpose of the expedition. It was therefore with surprise and some consternation that the others realized where they were as they rode into the courthouse square and halted. A buzz of excited whispers rose from the men. "That's right," Mosby assured them calmly. "We're in Fairfax Courthouse, right in the middle of ten thousand Yankees, but don't let that worry you. All but about a dozen of them are asleep. Now, if you all keep your heads and do what you're told, we'll be as safe as though we were in Jeff Davis' front parlor." He then began giving instructions, detailing parties to round up horses and capture any soldiers they found awake and moving about. He went, himself, with several men, to the home of a citizen named Murray, where he had been told that Wyndham had quartered himself, but here he received the disappointing news that the Englishman had gone to Washington that afternoon. A few minutes later, however, Joe Nelson came up with a prisoner, an infantryman who had just been relieved from sentry duty at General Stoughton's headquarters, who said that there had been a party there earlier in the evening and that Stoughton and several other officers were still there. Mosby, still disappointed at his failure to secure Wyndham, decided to accept Stoughton in his place. Taking several men, he went at once to the house where the prisoner said Stoughton had his headquarters. * * * * * Arriving there, he hammered loudly on the door with a revolver butt. An upstairs window opened, and a head, in a nightcap, was thrust out.