Final answer:
From Walt Whitman's description, it is clear that the Union forces faced a significant defeat at the First Battle of Bull Run, resulting in a chaotic retreat and severe blow to morale.
Step-by-step explanation:
From Walt Whitman's account, it can be inferred that the First Battle of Bull Run was a disastrous defeat for the Union troops. Whitman describes the Union soldiers as baffled, humiliated, and panic-struck as they retreated the twenty miles back to Washington, D.C., indicative of a chaotic and demoralizing loss. The Union's goal to quickly end the rebellion by capturing an important railroad center at Manassas Junction ended in failure, shattering the Northern morale and dispelling the early belief that the Civil War would be short and decisive.
The First Manassas, or the First Battle of Bull Run, was marked by high expectations of a swift Union victory. However, the battle unfolded differently than expected with the Confederate forces ultimately claiming victory. The result was a significant psychological and military setback for the Union, resulting in retreated Union forces and shocked Washington socialites and politicians who had anticipated observing an easily-won conflict. The military confrontation solidified the harsh reality of a lengthy and gruesome war ahead.