Take a gander at this picture. It is rapidly becoming an iconic image of protest.

Police in Baton Rouge, La., were all suited up for the worst when demonstrators marched to protest the shooting death of a young black man by a police officer.

Why has this photo gone viral? Beats me. Perhaps it speaks to the fragile line between civil disobedience and armed conflict.

Yes, it does remind me of a couple of other historic images:

We have this one, shot in 1989 as demonstrators marched through Tiananmen Square in Beijing to protest the dictatorial rule of the People’s Republic of China.

The man standing in front of the row of tanks would move back and forth, blocking the tanks’ progress.

I’ve heard reports over the years that the protester was arrested and has since died.

Then there’s this one:

Those of us of a certain age and older remember this image and what it represents.

The Vietnam War was raging and it wasn’t going too well for us politically. Marchers took to the streets and at times confronted armed troops. Some of the marchers reacted badly. Others reacted the way this young man did.

Photojournalists were able to capture this — and many other — images. They are saved for posterity.

It does us well to look back at them to remind ourselves of how we arrived at the present day.