THE FATE OF UKRAINE may have been decided by the time you read this, but that’s no excuse to shy away from acknowledging Russia’s lawless assault on that country, even from people who’ve never been there, like me.

In plenty of other places around the world civilian populations are arguably facing the same or even worse conditions. For me, what made the situation in Ukraine different was Vladimir Putin’s threat to use nuclear weapons in order to claim victory in this cruel invasion of a sovereign neighbor.

My father served in the U.S. Army throughout World War II always on assignments in the United States. A few weeks after the Nazi surrender he arrived in Germany. He was an engineer and worked on assessing the physical damage done by the Allied bombing. He returned to civilian life a few years later, but he remained in the Army Reserve.

One of my earliest memories is of him leaving home for a couple of weeks every summer for “maneuvers.” In the mid-1950s my mother, sister, brother and I tagged along to Fort Rodman in New Bedford, Massachusetts. We stayed in a dark, seaside cabin nearby as Dad reported for duty. But one day near the end of the trip my father asked if I’d like to visit the officers’ barracks, a long wooden building at the fort. When we arrived it was empty. My father showed me his “room,” with a cot and a chair. He told me to wait for him. He would be back. Then he left. There was nothing to look at. But down the hallway there were voices. I waited as long as I could.

This room was brightly lit. The walls and a row of tables were covered with maps. The maps were covered with sheets of clear plastic. My father was holding a pen. I asked him what place the map nearest us showed. “Warsaw,” he said. “It’s in Poland.”

I remember looking at Warsaw. Somebody had drawn concentric circles radiating outward from the center toward the edges of the wall. “What are these?”

He told me they showed the damage that would be done by an atomic bomb.

“Colonel!” said a tall man with very short hair, “It is Not appropriate for that child to be here.”

I spent a few hours more in his barracks room and much more time since then thinking about nuclear weapons. I prefer to believe that the training senior officers like my father received alerted them to the horrors these weapons inflict. I hope now that their Russian counterparts have a similar appreciation for the importance of their task.

From what scholars and diplomats familiar with contemporary Russia are saying, the unthinkable has become possible. Putin has gone from brutal dictator to an evil presence. As yet, no authority inside Russia has emerged to restrain him.

Undoubtedly, throughout our military, plans to respond to Putin’s threat are being reviewed, perhaps updated. And what keeps occupying my thoughts is my brief visit to the Fort Rodman map room—rooms filled with decent men and women planning for an event inappropriate for any child to know.