Question: Which of the serious defeats for the Union came first in the American Civil War: the Battle of Chickamauga or the Battle of Fredericksburg?

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Battle of Aquia Creek: The Battle of Aquia Creek was an exchange of cannon fire between Union Navy gunboats and Confederate shore batteries on the Potomac River at its confluence with Aquia Creek in Stafford County, Virginia.  The battle took place from May 29, 1861 to June 1, 1861 during the early days of the American Civil War.  The Confederates set up several shore batteries to block Union military and commercial vessels from moving in the Chesapeake Bay and along the lower Potomac River as well as for defensive purposes.  The battery at Aquia also was intended to protect the railroad terminal at that location.  The Union forces sought to destroy or remove these batteries as part of the effort to blockade Confederate States coastal and Chesapeake Bay ports.  The battle was tactically inconclusive.  Each side inflicted little damage and no serious casualties on the other.  The Union vessels were unable to dislodge the Confederates from their positions or to inflict serious casualties on their garrisons or serious damage to their batteries.  The Confederates manning the batteries were unable to inflict serious casualties on the Union sailors or cause serious damage to the Union vessels.  Soon after the battle, on Sunday, July 7, 1861, the Confederates first used naval mines, unsuccessfully, off the Aquia Landing batteries.  The Confederates ultimately abandoned the batteries on March 9, 1862 as they moved forces to meet the threat created by the Union Army's Peninsula Campaign.  The U. S. National Park Service includes this engagement in its list of 384 principal battles of the American Civil War.

Battle of Natural Bridge: The Battle of Natural Bridge was a battle during the American Civil War, fought in what is now Woodville, Florida, near Tallahassee, on March 6, 1865.  A small band of Confederate troops and volunteers, mostly composed of teenagers from the nearby Florida Military and Collegiate Institute that would later become Florida State University, and the elderly, protected by breastworks, prevented a detachment of United States Colored Troops from crossing the Natural Bridge on the St. Marks River.  The Natural Bridge is a one-quarter mile long stretch along which the St. Marks River runs underground, after dropping into a sinkhole.  This action prevented the Union Army from capturing the Florida capital and made Tallahassee the only Confederate capital east of the Mississippi River not to be captured by Union forces during the war.  The battle has been described as the last Confederate victory in the American Civil War, and it was the second largest American Civil War battle in Florida.

Battle of Chickamauga: The Battle of Chickamauga, fought on September 18–20, 1863 between Union and Confederate forces in the American Civil War, marked the end of a Union offensive in southeastern Tennessee and northwestern Georgia — the Chickamauga Campaign.  It was the first major battle of the war fought in Georgia, the most significant Union defeat in the Western Theater, and involved the second-highest number of casualties after the Battle of Gettysburg.

Chickamauga Campaign: The Chickamauga Campaign of the American Civil War was a series of battles fought in northwestern Georgia from August 21 to September 20, 1863, between the Union Army of the Cumberland and Confederate Army of Tennessee.  The campaign started successfully for Union commander William S. Rosecrans, with the Union army occupying the vital city of Chattanooga and forcing the Confederates to retreat into northern Georgia.  But a Confederate attack at the Battle of Chickamauga forced Rosecrans to retreat back into Chattanooga and allowed the Confederates to lay siege to the Union forces.

Ambrose Burnside: Ambrose Everett Burnside (May 23, 1824 – September 13, 1881) was an American soldier, railroad executive, inventor, industrialist, and politician from Rhode Island, serving as governor and a United States Senator.  As a Union Army general in the American Civil War, he conducted successful campaigns in North Carolina and East Tennessee, as well as countering the raids of Confederate General John Hunt Morgan, but suffered disastrous defeats at the Battle of Fredericksburg and Battle of the Crater.  His distinctive style of facial hair became known as sideburns, derived from his last name.  He was also the first president of the National Rifle Association.

Battle of Calcasieu Pass: The Battle of Calcasieu Pass was a minor skirmish fought on May 6, 1864, at the mouth of the Calcasieu River in southwestern Louisiana, during the American Civil War.  It resulted in a Confederate victory.  The participants of the battle were Lt. Benjamin Loring and Lt. C. W. Lamson on the Union’s side, and Col. W. H. Griffin on the Confederate side.  The union brought along two naval vessels, the U.S.S Wave and the U.S.S Granite City.  The U.S.S Wave did not prove too effective during the battle and was captured early on, it was soon turned into a Confederate cargo ship.  The U.S.S Granite City was originally a confederate blockade vessel, but was captured in 1863 by the U.S.S Tioga (Union).  The U.S.S Granite City was now back in the hands of the Confederates.  Captain Joseph A. Brickhouse, a Confederate veteran, said, “We fought in the open prairie, bringing on the attack with four small pieces of artillery and less than 300 infantry, poorly armed, attacking in the open prairie two such boats as the Granite City and Wave - Union gunboats - and capturing them after an action of less than two hours and 40 minutes duration.”  He described his own forces (Confederate) as unprepared, and he stated that they still had an easy battle that was short in duration.  The Confederate forces in this battle were split up into five battalions.  The first battalion was Creuzbauer's Battery, 5th Texas Artillery.  Every soldier in this battalion was born in Germany, and they all migrated to the U.S during the Civil War.  The second battalion was named Griffin’s Battalion, and was led by Col. William Henry Griffin.  The third battalion was Spaight’s Battalion, led by Lt. Col. Ashley W. Spaight.  And the final one was Daly’s Battalion, the only cavalry unit in the battle.  The U.S.S Wave and the U.S.S Granite City received orders to proceed to Calcasieu Pass.  When they arrived, immediately bombed an abandoned Confederate fort at the mouth of the river.  The Gunboats were sent with money to purchase cattle from local southern farmers.  The U.S.S Granite City ended up stealing cattle and horses from multiple farms.  This prompted a Confederate attack.  The local Confederate forces arrived quietly and prepared for a night-time attack on the Union forces.  When the Union went to sleep, they let less-experienced soldiers man the guns.  The Confederates seized the opportunity and moved their cannons closer.  The cannons lined up 1,000 yards away from the gunboats, while the cavalry and foot-soldiers advanced.  Numerous cannon shells penetrated the gunboat’s hulls.  While the cavalry and foot-soldiers moved in, the artillery advanced as well, and finished off the vessels.  On May 8th, Ella Morse, a Union Supply ship did not know of the Union casualties.  Then brought moved up all the way to the other ships with supplies.  When she noticed that confederates were manning the guns it was too late.  They gunned the ship down.  The Union Forces suffered many casualties.  They lost the Ella Morse, the U.S.S Granite City, the U.S.S Wave, and the U.S.S New London.  On the other hand, the Confederates did not lose too many soldiers.  The Confederates only suffered a few men from each battalion.

Battle of Fredericksburg: The Battle of Fredericksburg was fought December 11–15, 1862, in and around Fredericksburg, Virginia, between General Robert E. Lee's Confederate Army of Northern Virginia and the Union Army of the Potomac, commanded by Major General Ambrose Burnside, as part of the American Civil War.  The Union Army's futile frontal attacks on December 13 against entrenched Confederate defenders on the heights behind the city are remembered as one of the most one-sided battles of the war, with Union casualties more than three times as heavy as those suffered by the Confederates.  A visitor to the battlefield described the battle to U.S. President Abraham Lincoln as a "butchery."

Battle of Stones River: The Battle of Stones River or Second Battle of Murfreesboro, was fought from December 31, 1862, to January 2, 1863, in Middle Tennessee, as the culmination of the Stones River Campaign in the Western Theater of the American Civil War.  Of the major battles of the Civil War, Stones River had the highest percentage of casualties on both sides.  Although the battle itself was inconclusive, the Union Army's repulse of two Confederate attacks and the subsequent Confederate withdrawal were a much-needed boost to Union morale after the defeat at the Battle of Fredericksburg, and it dashed Confederate aspirations for control of Middle Tennessee.

20th Indiana Infantry Regiment: The 20th Indiana Volunteer Infantry Regiment was an infantry regiment that served in the Union Army during the American Civil War.  The Regiment was officially raised on July 22, 1861, by William L. Brown, the first Colonel of the Regiment, in response to President Lincoln's call for volunteers.  At the time of muster, the regiment had 9 fighting companies lettered A-K along with a staff company for a total of 10 companies, roughly 1000 men.  The 20th Indiana saw engagements in most of the major battles of the American Civil War, including the action between the first ironclads at Hampton Roads, the Battle of Fredericksburg, the Battle of Gettysburg, and the Siege of Petersburg.  The Regiment was part of the 1st Brigade, 3rd Division, III Corps for the duration of the war.

Presbyterian Church of Fredericksburg: Presbyterian Church of Fredericksburg is a historic Presbyterian church located southwest of Princess Anne and George Streets in Fredericksburg, Virginia.  It was built in 1833, and restored in 1866 after being badly damaged during the American Civil War.  It is a rectangular brick church building of Jeffersonian Roman Revival design.  The church has a triangular, gable-end pediment surmounting a wide entabulature which surrounds the entire building.  The front facade features four wide, wooden Doric order pilaster, and two round Doric order columns each set at the frontt edge of the recessed portico.  During the American Civil War the church served both Union and Confederate soldiers and it was in this building that Clara Barton came to nurse the wounded after the Battle of Fredericksburg in 1862.

Supporting paragraphs: Battle of Chickamauga Battle of Fredericksburg
Answer: Battle of Fredericksburg