GETTYSBURG & ANTIETAM (SHARPSBURG).  These were the two bloodiest battles of the war. The three-day Battle of Gettysburg (Pennsylvania, July 1863) saw more casualties than any American wartime event until World War I. Casualties  totalled more than 46,000 on both sides. The Battle of Antietam (or Sharpsburg, Maryland, September 1862) was the single bloodiest day of the war, with more than 22,000 total casualties. Both battles were triggered by Confederate invasions of Union states by General Robert E. Lee's Army of Northern Virginia. Antietam was considered a strategic Union victory when Lee's army retreated back across the Potomac River. Gettysburg was an overwhelming Union victory, climaxed when Lee's monumental thrust against the Union center with 15,000 men was repulsed with heavy losses. In both cases, the Confederate army had hoped to reach Baltimore and possibly Washington, D. C.

1ST BATTLE OF BULL RUN (MANASSAS).  There really aren't too many similarities between 1st Bull Run and the aforementioned battles. First Bull Run was an overwhelming Confederate victory which saw Union troops breaking and retreating in disorder back to Washington. Perhaps the single similarity was the distinguished performance by Confederate General Thomas "Stonewall" Jackson, who earned his nickname with a solid defensive stand at Bull Run; at Antietam, his fast-marching infantry arrived from the previous capture of Harper's Ferry just in the nick of time to beat back a Union attack and end the day's long fighting.

Battles of First Manassas, Sharpsburg, and Gettysburg.

Similarities: C.S.A. was outnumbered by U.S.A. at all three battles.

Differences:  Each battle had a different outcome;, C.S.A. won one, one was a draw, U.S.A. won one.

At First Bull Run (First Manassas), the troops on both sides were inexperienced at war.  Gen. McDowell, U.S.A., was a good general, but his inexperienced troops broke and ran, so that he lost the battle.  Gen. J. E. Johnston, C.S.A., was also a good general.  The C.S.A. troops were not experienced, but they were fighting on their own soil for their homes and hearths, so they did not break and run.  There were charges by the U.S.A. and countercharges by the C.S.A.

At Antietam (Sharpsburg), a good general (Lee, C.S.A.) faced a poor general (McClellan, U.S.A.) and fought his vastly superior army to a draw.  McClellan was a good organizer and a good trainer of troops, but a very poor fighting general.  The U.S.A. charged across open ground at the C.S.A. which was positioned on slightly higher ground.

At Gettysburg, the troops on both sides were experienced at war and both sides were led by good generals.  The U.S.A. greatly outnumbered the C.S.A. at this battle.  The C.S.A. charged across open ground at the U.S.A. which was positioned on a hill top.