(A) Andrew Jackson
(B) ** John Pope
(C) Stonewall Jackson
(D) McClellan
EXPLANATIONS BELOW
Concept note-1: -As a large Union force commanded by John Pope waited for George McClellan’s Army of the Potomac in anticipation of a combined offensive, Confederate General Robert E. Lee decided to strike first. Lee sent half of his Army of Northern Virginia to hit the Federal supply base at Manassas.
Concept note-2: -On July 21, 1861, in the first major land battle of the Civil War, a large Union force under General Irvin McDowell is routed by a Confederate army under General Pierre G.T. Beauregard.