African American Union Troops under Colonel James Montgomery's command attacked plantations along the Combahee River in South Carolina on June 2, 1863. After learning where the Confederate mines were located along the river, Harriet Tubman led three Union ships around them as they navigated the waterway, liberating slaves as they went. Steamboat whistles alerted local slaves to the approaching freedom as an armed assault on the plantations got under way. From the plantations to the steamboats, the slaves fled. Because of Tubman's bravery and leadership, more than 750 slaves were set free. It is acknowledged that Tubman was the only woman to command a military operation during the Civil War.