On Jan. 24, a slave named Harry escaped to the Union picket line. Rather than return him to his owner, as other officers might have, Captain Heine took him on as a guide and servant. He gave him a uniform, a pistol, a sabre and “a good horse.” A full year before the Emancipation Proclamation or the enlistment of black soldiers, Harry became the first black cavalryman of the war. He knew every road and path in the area, and, according to Sneden, “would fight to the death before allowing himself to be captured.”
This intelligence on the ground was augmented by aerial reconnaissance. In late January, Thaddeus Lowe used a balloon to survey the landscape, and noticed that Confederates were building earthworks to the south (marked in red on the map). Heine immediately organized a raid on Colchester with two goals in mind: to measure these earthworks that Lowe had spotted, and to capture the rebel smugglers. On the night of Jan. 29, he took 50 men from the 37th New York, with Sneden and Harry to guide them. Just five days earlier, Harry had been a slave; now he was leading an armed raid against his former owners.