Great different take on the topic, while still meeting the challenge. I would have been tempted to reduce the depth of field, making the line of police sharp, the background less focussed, and the foreground less focussed. I think this would have added to it, removed clutter from the background, and given more of a sense of movement and people numbers to the crowd at the front, and more of a sense of being in the crowd for the viewer.
If the immovable symbols are the police then the focus looks good. I'm assuming though that the immovable symbols are the peace signs, in which case the photo would have been better if the focus was on one of the peace symbols (like the person with the tan jacket) and the police were in the background with a shallow DOF. Still a nice photo though.
Nice interpretation of the them. The repeated pose of the police adds an interesting rhythm to the shot, and they communicate a sense of immovability (?) well.
I wish DPC had more of this type of image. The title shows the connection to the challenge, but I feel you lost an opportunity to give a bit of necessary background.
Not sure how well this will do in the challenge. But for me this photo has real impact. Could be in any paper around the word. These can be dangerous shots too. Too easy for the photographer to get caught up by either side if things start going bad. Nice capture.