“You are about to embark upon the Great Crusade, toward which we have striven these many months. The eyes of the world are upon you.”

— General Dwight D. “Ike” Eisenhower, addressing troops prior to Operation Overload

One of the greatest military achievements ever occurred 81 years ago today. Code named Operation Neptune — the Naval component of Operation Overlord — and usually referred to as D-Day, June 6, 1944 is when the largest seaborne invasion in history began .

D-Day was a massive invasion of Allied forces against the Nazi tyranny. Planning began in 1943. Think of what went into pulling it off: the men, the machinery and the sheer might needed. The sheer logistics! Even the weather, phases of the moon and tides had to be factored. And keeping it all a secret.

D-Day was the invasion of the beaches at Normandy in northern France by troops from the United States, Canada, the United Kingdom and other countries during World War II. France at the time was occupied by the armies of Nazi Germany. The amphibious assault landed some 156,000 Allied soldiers on the beaches of Normandy by the end of the day.

Despite their success, some 4,000 Allied troops were killed by German soldiers defending the beach sectors named Omaha, Utah, Gold Juno and Sword. German gun encampments atop the shores cut many soldiers down. Mines also took a toll. Parachutists were killed behind enemy lines.

According to History.com, at the time, the D-Day invasion was the largest naval, air and land operation in history, and within a few days about 326,000 troops, more than 50,000 vehicles and some 100,000 tons of equipment had landed. All of those who perished did not die in vain.

The sacrifices paved the way for the liberation of German-occupied France and then Europe from Nazi control. D-Day indeed laid the groundwork for the Allied victory on the Western Front. By August 1944, all of northern France had been liberated.

You probably have watched the documentaries and specials on TV about one of the biggest moments in the history of our nation. Some will be on today as they should be. Maybe you grimaced and watched the Normandy beach landing depicted in “Saving Private Ryan” — acclaimed for its accuracy in detailing what happened that fateful morning an ocean away. If you are fortunate you may even know or did know someone who actually participated in the invasion.

And, sadly, with Father Time being who he is, there aren’t too many left who actually fought on those beaches. If unfamiliar with D-Day, grab a book or do some online research. You will become a better American for it. And, yeah and for sure: shame on those so-called “Americans” who could care less about significant moments in our nation and sacrifices made to preserve our freedom. “Our” meaning each and every single one of us.

Most of us weren’t around in 1944. But a big reason we are free today was the success of the D-Day invasion. The least we can do is remember it on this day each and every year and honor the memories of all involved and all who sacrificed. Historians often refer to D-Day as the beginning of the end of World War II. That should never be forgotten. Especially as time — much like a crack infantry battalion in lockstep — goes marching onward.