The post is not a tweet by CNN. It is a digitally altered image.
We conducted a Twitter advanced search and did not find any such tweet on CNN's Twitter page. We also discovered the viral image through a reverse image search, which came from an article in The Times on August 26, 2018. The article was a photography feature on Ukrainian children aged seven to 15 years, who were spending their school holidays at summer camp, learning military skills.
According to Reuters, a CNN spokesperson confirmed that "no such tweet was shared" by the organization. Therefore, it's evident that the image in circulation is digitally altered and is not a tweet by CNN. We mark this claim as false.