During World War I, groups of 20–30 American soldiers sometimes packed into a single shell crater while preparing to advance. If enemy artillery or machine-gun

During World War I, groups of 20–30 American soldiers sometimes packed into a single shell crater while preparing to advance. If enemy artillery or machine-gun fire struck their position, the entire group could be killed in an instant. [▻](https://video.twimg.com/amplify_video/2105885558949945345/…