What identifies the soldiers on the river bank as union soldiers?

The soldiers on the river bank can be identified as Union soldiers by their distinctive blue uniforms, which were standard for Union forces during the Civil War. Additionally, they may carry specific insignia or flags associated with the Union Army, such as the Stars and Stripes or the Union's official emblem. The presence of their equipment and weaponry, which align with Union specifications, further confirms their identity. Lastly, their conduct and organization may reflect the strategies and tactics employed by Union troops.