WARSAW— American millennials have a lot of complaints about their lot in life. So here’s a question for them: When is the last time you had to walk through a sewer waist-high in human filth, choking on the toxic ammonia, yet unable to cough for fear of alerting the Nazi SS soldiers on the street above — knowing that if you did, they would open a manhole cover and toss in grenades or poison gas to kill you?

Marc Thiessen

Here in Warsaw 75 years ago, teenagers did exactly that. Last week, surviving members of the resistance gathered in the Polish capital to mark the anniversary of the Warsaw Uprising, when the underground Home Army rose up, freed the city from Nazi occupation and held it for 63 days.

I came here with my 91-year-old mother, who fought in the uprising. Before the insurgency began, she served as an underground courier, carrying radios and messages across the city. She and her fellow girl scouts would sneak out of their homes after curfew — a crime punishable by death — to leave flowers at monuments to Polish heroes or paint anti-Nazi graffiti on walls. And during the uprising itself, she would dodge German sniper fire as she ran across barricades to carry orders and weapons to soldiers fighting on the front lines.

Only about a quarter of the Poles had weapons; many went into battle armed with little more than rocks. Kids as young as 10 or 11 would sneak up to German tanks and set them on fire using gasoline bombs. The Nazis responded with unbridled fury. In the city’s Wola district, they executed more than 50,000 civilians. By the time the Home Army was forced to surrender, nearly 200,000 civilians and 16,000 soldiers were dead, and 80% of the city was destroyed.

In our colleges and universities, first millennials and now their Generation Z successors have demanded “emotional safety,” insisting on “safe spaces” and “trigger warnings” to protect them from ideas they don’t like, because they tell us that “words are violence.” No, they are not. Violence is SS officers using flamethrowers to clear buildings. Violence is defenseless civilians being put in front of Nazi Panzers as human shields. During the Warsaw Uprising there were no “safe spaces” — battles were literally fought house to house, room to room. There were no “trigger warnings” — only Germans pulling their triggers as they executed civilians and prisoners of war lined up on street corners.

In Poland, young people understand this. It was remarkable to watch how young Poles embraced the nonagenarian insurgents. More than 10,000 scouts and volunteers stepped forward to help with the commemorations — pushing the aged partisans in their wheelchairs, bringing them cups of water and soaking in their stories. On Aug. 1, at exactly 5 p.m. — the “W” hour, when the uprising began — the entire city came to a halt. As air raid sirens wailed, people poured onto the streets, setting off flares and car alarms, honking their horns — and chanting in unison, “Heroes, we will not forget you.”

I brought my kids — ages 17, 16 and 13-year-old twins — here to witness this. I wanted them to see with their own eyes what real adversity, sacrifice and heroism look like. I wanted them to put their fingers in the bullet holes that still mark the walls where the Nazis executed children their age. I wanted them to understand that these horrific events happened within the lifetimes of their immediate family, and that they must never take for granted the freedom, peace and security they enjoy.

Most of all, I wanted them to realize that they are growing up in what is, quite literally, the greatest time in the history of man to be alive. At no time since human civilization began has there been more prosperity, more freedom, more upward mobility, better life expectancy and less poverty, disease, hunger, illiteracy or violent crime than there is today. This unprecedented moment was purchased for them by the sacrifices of a generation before them — men, women and even children their ages, who took up arms, stood up to evil and gave their lives so that they could live in a world of peace, liberty and limitless opportunity.

Their job is to never forget that sacrifice, and to uphold the values for which they fought. And most of all, to be grateful they never had to trudge through a sewer to avoid Nazis.

Marc Thiessen is a columnist with  the Washington Post. Follow him on Twitter, @marcthiessen.