Palestine, July 21 -- I was working as an emergency doctor for Doctors Without Borders/Medecins Sans Frontieres (MSF) in the emergency department of Al-Aqsa Hospital in Deir al-Balah, in Gaza, Palestine, when two young girls were brought in, one about 7 years old, the other 5. The older one had lost her left arm from the shoulder. The younger one was covered in blood, but I couldn't immediately identify her injury, so I focused on her.

At first, I was hopeful, because she was on her back, and I couldn't see any signs of injuries. I thought that the blood belonged to her sister. But when I turned her over, her entire right side was open. Her lungs were exposed, covered in shrapnel and dirt, moving fast with her breathing.

I took her to the...