Editor’s note: This story serves as the introduction to our coverage of important moments in both the American struggle for independence and the Civil War as significant dates overlap.

This week, 157 years ago, the Battle of Gettysburg was fought. The Battle of Gettysburg was not only the largest battle of the American Civil War, but was also the largest battle on American soil.

The Grand Army of the Potomac and the Army of Northern Virginia clashed for the three bloodiest days in U.S. history from July 1-3, 1863. The Battle of Gettysburg is largely regarded as the turning point of the American Civil War.

Up to July 1, the Confederate Army of Northern Virginia had seen significant success in the Eastern theatre of the war, while the Western theatre was moving at a sluggish pace until Union General Ulysses S. Grant was able to take Vicksburg, which would be the beginning of the end for the Confederacy in the West.

Confederate commanding General Robert E. Lee had won a decisive battle at Chancellorsville, Virginia. Following the victory at Chancellorsville, Lee took his army north, out of Virginia and into Pennsylvania.

Lee’s goal was to take economic pressure off of Virginia and fight an offensive campaign in North. Lee hoped bringing his army north and closer to major Union cities like Boston, Washington, would apply pressure to ongoing peace talks to bring the war to an end.

Lee’s invading army was comprised of some 71,000 troops, which he hoped would be enough to crush the Army of the Potomac, which was in relatively low spirits after Chancellorsville.

Lee was marching into Pennsylvania rather blind, however. The majority of his cavalry, under General Jeb Stuart, was far past his own lines, and did not send adequate reports to Lee on the size of the Union Army.

The Army of the Potomac had just days ago transferred command to General George Meade. Lee expected Meade to be terribly cautious, being new to such a large command, an army that stood at some 93,000 strong.

In the three days to follow, Lee hoped his significantly smaller force would be able to roll over the Army of Meade, apply pressure to Washington, and in that same stroke, prove to European powers that the Confederate States of America were legitimate, and would stand.

A decisive victory at Gettysburg would be what it would take for Britain and France to recognize the Confederacy and as the South hoped, send in much needed military and financial support.

Should Meade and the Army of the Potomac win, it would be a devastating loss to not only Lee’s numbers, but morale, and hopes of European intervention.

July 1 through July 3, by Gettysburg and in conjunction with the siege of Vicksburg, would tell whether the Confederacy would stand or fall.