Had Lee not been so operationally weakened by his defeat at Gettysburg, he would likely have been able to continue offensive operations and conceivably have brought Washington, DC, itself under assault; the entire course of the war would have taken radically different trajectory. However the war might have ultimately turned out, had Lee continued the offensive in the North beyond Gettysburg, it is likely that Atlanta would not have fallen by the summer of 1864 and Lincoln been defeated by McClellan. Without the moral force of Lincoln at the helm, the Thirteenth Amendment would most certainly not have been passed.

The tide of slavery was already waning in the world at the time of the Civil War, and it is a virtual certainty that the wretched institution would have ended at some point in American history, even without Lincoln. But at what cost? How many more years or decades would have passed before freedom was won for black Americans? Those answers are impossible to answer, but one thing is certain. As much difficulty as the country has with race relations today, they are nothing in comparison to what we would still be facing had freedom not come until sometime in the twentieth century.

Gettysburg was a major battle that inflicted grievous wounds on both the North and the South. Though even at the time the Union was recognized at having come out on top, their losses led to discouragement and discontent at the ambiguity of the outcome throughout the North. Yet the slight margin of victory proved to be just enough to allow Sherman’s troops to defeat the Confederacy in Atlanta the next year. One of the enduring lessons of Gettysburg is that one never knows how consequential events may prove to be in the future, even when the results are mixed and messy.

Daniel L. Davis is a retired U.S. Army colonel who served multiple tours in Afghanistan. He is a senior fellow with Defense Priorities. Follow him on Twitter @DanielLDavis1.