The answer is "<span>Union forces staged a surprise attack but were forced to retreat".</span>
The <span>First Battle of Bull Run is known by two names given to it by both the participants,
the stated name was used by the Union forces while the name used by the Confederate
forces was Battle of First Manassas. It was fought in 1861 and is considered the
first major battle of American Civil War. Confederate won this battle and Union
forces retreated.</span>