Complex sentence: It was the first division to pierce the famed German Hindenburg Line of defense, and the 32nd then adopted its shoulder patch; a line shot through with a red arrow, to signify its tenacity in piercing the enemy line.
Split into simpler sentences: It was the first division to pierce the famed German Hindenburg Line of defense. Its shoulder patch became a line shot through with a red arrow, to signify its tenacity in piercing the enemy line.