This is the 156th anniversary of the third and last day of the Battle of Gettysburg. The 1993 movie that portrayed this pivotal battle — starring Jeff Daniels, Tom Berenger, Martin Sheen, and Sam Elliot, among others — is something that Americans probably need to re-watch, and soon.

A quick historical reminder is necessary: The Battle of Gettysburg took place over two years after the attack on Fort Sumter. We as a country need to remember the heroism from that battle. Whether it was John Buford’s brilliant efforts to delay Confederate forces on the first day, Joshua Lawrence Chamberlain’s stand on Little Round Top on the second day of the battle, or Winfield Scott Hancock famously declaring on the third day, “There are times when a corps commander’s life does not count.”

At the time, it was one of the largest battles in the Western Hemisphere, and these days, not many Americans are as familiar with this seminal event in our history. We should remember this battle for the same reason we remember the Battle of Midway, because this battle matters — or should matter to Americans.

This is not just due to the fact that Gettysburg ranks as a singularly bloody battle. At least 46,000 troops were killed, wounded, or missing across those three days of fighting that involved more than 170,000 troops on both sides. To put that into perspective, the entire crew and air wing on a Nimitz-class carrier comes to around 6,000 — so it was enough to man seven carriers — with 4,000 people left over. It’s a staggering total.

While in some ways, Gettysburg overshadows the vastly more important Vicksburg Campaign, which ended on July 4 with the surrender of Vicksburg, it also represented the high-water mark of the Confederacy. After Gettysburg, the Confederacy was placed purely on the defensive. It still took nearly two years to end the Civil War, leaving more than 660,000 dead. It remains the highest total of wartime dead in America’s 243-year history.

The fact is, the Civil War is an era we should remember, because the failure to learn from history all too often dooms us to repeat it.

As Byron York noted in the Washington Examiner, recent events are taking a terrifyingly toxic turn. Some of these have seen precursors that go back a long time, but it has ramped up to a level that could send things out of control. But the efforts to exclude conservatives from some professions, as well as the targeting of not just freedom of speech but freedom of the press, point to an effort aimed at anyone who doesn’t accept certain left-wing paradigms.

These days, the expression of disagreement with the Left on hot-button political issues becomes a license to try to destroy lives. This is a situation that cannot end well. Perhaps re-watching Gettysburg and seeing the horrors of the Civil War can help avoid a very bad outcome.