On April 25, Banks' Union force occupied Harrisonburg. Jackson withdrew to Swift Run Gap (about 20 miles East of Harrisonburg). This put him in a position to outflank Banks if the Union forces moved any further south and allowed him to stay in contact with Ewell's Confederate division if he needed support. Meanwhile a Union brigade under Robert H. Milroy was at the village of McDowell, Virginia which threatened Jackson's supply depot at Staunton. Jackson left Ewell at Swift Run Gap to move against Milroy. 