On July 6, 1864, Confederate cavalrymen crossed the Potomac River into Maryland as part of a 12,000 man force under Gen. Jubal A. Early, who planned to attack lightly defended Washington, D.C., and draw off part of the Union army menacing Richmond and Petersburg. Union Gen. Lew Wallace's force, however, delayed Early at the Monocacy River on July 9. Early then ordered Gen. Bradley T. Johnson's cavalry brigade to cut off Baltimore and Washington from the north and free 14,000 Confederate prisoners at Point Lookout, Maryland. After destroying the Northern Central Railroad bridge in Cockeysville, Johnson detached Maj. Harry Gilmor with 135 troopers to destroy the Philadelphia, Wilmington and Baltimore Railroad drawbridge over the Gunpowder River near Magnolia Station and Joppa. Gilmor arrived at the station at 8:30 A.M. on July 11 and captured a stopped northbound train from Baltimore, but after the engineer disabled the controls and fled, he burned it. An hour later a second train arrived and also fell into Gilmor's hands, along with Union Gen. William B. Franklin. Gilmor detrained the passengers, set the train on fire, and backed it onto the Gunpowder River bridge. Although the Union gunboat Juanita and detachments from Co. F, 159th Ohio National Guard, and the Delaware Volunteers guarded the bridge, they could not stop him. As the burning train engulfed the bridge in flames, Federal soldiers leaped into the river. A few uncoupled two cars and rolled them to safety, but the draw span soon collapsed and several cars plunged into the water.