Let this one sink in. 

By June 10, 1944, 70 years ago today and a mere four days after the start of the D-Day invasion of Europe, 15,000 Allied soldiers were either dead, wounded or captured by the enemy. 

We repeat: 15,000 Allied casualties, with more than 4,000 dead.

Yet, the charge to defeat the Nazis never faltered. For this, every person alive today owes a debt to the men and women who sacrificed so much 70 years ago.

At a sea-side ceremony last Friday in Normandy, President Barack Obama shared a portion of letter from a French citizen addressed to the president and all Americans:

“[We are] honored to welcome you ... to thank you again for all the pain and efforts of [the] American people and others in our common struggle for freedom.”

On such a momentous anniversary, the question often arises: How would we react under such worldwide threats? And what of citizens, would they so willingly rally around such a cause and keep faith in the midst of so much death and destruction?

Pondering the answers would take days and fill countless books. The truth is that our times are not their times. Our challenges are not theirs.

The Sept. 11, 2001, attacks on the Twin Towers and the Pentagon and the subsequent fight to root out and foil the plots of jihadists is the closest comparison. What followed in the days and weeks after 9/11 were pledges of unity. A French newspaper declared, “Nous sommes tous Américains.” (Translation: “We are all Americans.”)

Yet, the good feelings and, more importantly, the unified agreement on next steps did not hold. It’s easy to blame America’s leaders in the White House and Congress, as they inserted the nation into first one and then another war without clear exit strategies.

These leaders missed a moment to ponder our footprint across the globe.

Lost were opportunities to reach out to a seething Middle East, one that resented U.S. actions that often manipulated and disregarded the people of the region. We failed to thoughtfully consider how the U.S. arming of rebels in Soviet-controlled Afghanistan in the 1980s set off a chain of events that resulted in 9/11. We ignored our role in supporting Iraq’s Saddam Hussein during his long war with Iran, a dictator who used chemical weapons on his own civilians.

Yet, citizens aren’t completely off the hook. We can only imagine a time when products such as tires, clothing and food were rationed in support of a war effort. How long would Americans stand for that today? Not very long, we’d guess.

For now, it might be best for Americans to offer thanks and gratitude to their forebearers who were up to the challenges presented during World War II. Because of them, we are free today.