Traverses were intended to protect defenders from incoming fire that swept along the length of a line, rather than hitting it head-on. On battlefields where long strings of entrenchments stretched for miles, they often snaked along without much regard for linear precision. That meant that the opposing enemy lines might, in some spots, be situated with an opportunity to fire down the length of the defenders’ primary line. The presence of traverses allowed the defenders to receive protection from that down-the-line firing, giving them protection from three different directions if necessary.
Some of the best traverses on field fortifications in Virginia survive at the North Anna battlefield, north of Richmond, and at Cold Harbor. This map of the Cold Harbor battlefield is enlarged to show a section of the fortifications where traverses clearly are visible on both the Union and Confederate lines. It is easy to see from the map how exposed both armies would be to down-the-line firing, were it not for the presence of traverses.