President Lyndon B. Johnson addresses the nation in a radio and television broadcast from the White House on March 31, 1968. (AP)

Patti Davis is the author of, most recently, “The Earth Breaks in Colors” and is the daughter of Ronald and Nancy Reagan.

This is a story about a faraway war that tore apart a country. This country. Before our boys were sent off to fight in a place called Vietnam, most of us had never given any thought to that place. Once they started leaving, it was all we could think of. Families were bitterly divided, protesters chanted in the streets, and some Americans lit themselves on fire to protest a war that most of us didn’t even understand.

I was away at a coed boarding school in the 1960s, too young to go out in the street and chant, “Hey, hey, LBJ, how many boys did you kill today?” Unexpectedly, the war moved closer to me: A boy in my high school didn’t return after Christmas break, having decided to enlist in the Marines. He was 17, which was allowed if a boy had parental consent. I’d heard that he had a fraught relationship with his father, so apparently consent was easy for him to get. A friend of his told me he’d love to get some letters, and, being a budding writer, I was happy to take on the assignment. Our correspondence became a constant for the next few years of my life.

It offered me a window into the mind of a boy who was being methodically trained to hate the enemy so that he could be okay with killing them. But what started to haunt me, and stay with me, was the realization that war is complicated.

This seems a relevant observation now, since we have a president who effectively just ended a war via Twitter — you can’t get much more simplistic than that. He didn’t consult his military advisers or the Pentagon about pulling out of Syria; he didn’t weigh consequences or choices. He apparently just woke up, fixed his hair, picked up his phone and went on Twitter. A few days later, Sen. Lindsey O. Graham (R-S.C.) came over for lunch, suggested he slow it down and then reported that the president had said okay. If Ann Coulter calls next week and says he should stick to his original plan, he might say yes to that. After years of war, thousands of lives lost and thousands of people horribly wounded, a decision about war comes down to a whim and a lunch date.

Contrast all of that with the 1968 photograph of Lyndon B. Johnson in the Cabinet Room, slumped to the side with his head down as he’s listening to a tape sent by his son-in-law, who was serving in Vietnam. It’s the image of a president who felt the unimaginable burden of war, the responsibility that lay with him, the lives that hung in the balance because of his decisions. You can sense how burdened he is in that photograph.

My high school friend did two tours in Vietnam. He came back between tours and flew to Sacramento on a summer weekend to see me at the governor’s mansion and stay overnight. At dinner with my parents, he made a point of sounding very pro-war, repeatedly saying how proud he was to fight overseas for America. Late that night, I tiptoed across the hall, and we sat on his bed talking in whispered voices. “Why did you talk like that at dinner?” I asked him. “I know you’re not that gung-ho about this war.”

“It’s what your father wanted to hear,” he said. “And, besides, there’s a part of me that has to feel like that every time I pick up my weapon.”

We thought once that we’d try to become lovers, but there was a fury behind his kisses, a tensile rage in his hands, his arms. He scared me, and I said stop. War is complicated — it finds its way into the blood and bones of young men who once never thought they could kill another human being.

The men and women who put on uniforms, pick up weapons and go to battle deserve a commander in chief who understands there is nothing simple or easy about war. The decision to go to war, and the decision to end a war, should be the result of intense conversations, debates at the highest levels of government and many sleepless nights. Our soldiers’ lives, and the lives of our allies on the battlefield, are worth more than impetuous messages pared down to 280 characters.