Context (Source: History of the world by Andrew Marr - Episode 8)
This is a big story (The author indicates the Atomic bombing of Hiroshima). Let's try and bring it down in scale a bit.
It made me feel like it means "let's analyze (or let's talk) about it a little bit". After that, the author showed how people died in the World War Atomic bomb in Hiroshima.
This is a woman's watch, hands fused to the time of the blast. Around 400 young children were here with their ten teachers when the bomb went off, and all but one was burned to death immediately. In a three-mile radius of the blast, almost everybody suffered fatal burns,..
I've look up the phrase "Bring sth down" in many dictionaries but the meanings they give didn't fit to the documentary.