Stationed in the town of Fredericksburg, Lang's men stubbornly contested Federal attempts to lay pontoon bridges across the Rappahannock River.

Recovering from his wounds, Lang was promoted to colonel of the 8th Florida on April 30, 1863, and fought at the Battle of Chancellorsville, where his brigade commander, Brig.

On July 2, 1863, he attacked the center of the Union defensive line on Cemetery Ridge, advancing past the Codori farm before being repulsed by troops from the II Corps.

On the following day, the brigade supported Pickett's Charge, but failed to advance far under heavy fire from Lt. Col. Freeman McGilvery's line of artillery.

However, by the end of the war, Brevard having been captured, Lang was again leading the Florida Brigade, surrendering it at Appomattox Court House on April 9, 1865.

He served an eight-year tenure as Florida's Adjutant General during the administrations of Governors Perry and Fleming (1885–1894).