After the Civil War broke out in 1861, Massachusetts Gov. John A. Andrew, a fervent abolitionist, contacted his friend Tubman and told her that the Union forces needed her help. He arranged transportation for Tubman to travel to Hilton Head, South Carolina, where she went to work for Maj. Gen. David Hunter. Ostensibly, her mission was to help provide food and clothing to escaped slaves who were flocking to the Union Army's camps, but that seems to have been a cover story for her real work in gathering intelligence. With a budget of $100 in "secret service money," she recruited a small team of escaped slaves who were experienced riverboat pilots and knew every inch of the South Carolina coastline, and put them to work as scouts for the Union forces [sources: Winkler, Quinn].
After President Abraham Lincoln authorized the recruiting and deployment of African-American troops in the summer of 1862, Tubman and her spies provided intelligence for the new units. In January 1863, her team's spying helped Union forces evade Confederate guards and stage a nine-day covert operation to seize needed supplies. As historian H. Donald Winkler describes it, Tubman's scouts "evolved into a kind of special-forces operation for the black regiments," sneaking into enemy territory to gather information on their troop movements and fortifications.
In June 1863, according to Winkler, Tubman accompanied Union Col. James Montgomery and his forces up the Combahee River in the southern low country of South Carolina and helped lead a crucial raid. Tubman and her scouts sailed upriver and stealthily went ashore to talk to the slaves who'd placed mines in the water for Confederate forces, so they could map the locations, and locate the storehouses where the enemy kept their supplies. Then she helped guide the Union craft around the deadly mines. The resulting raid not only struck a devastating blow to the Confederate forces, but also resulted in freedom for 700 slaves — many of whom subsequently were recruited by Tubman to serve in the Union forces.