Herbert Cobb enlisted in the U.S. Army in 1916. He was sent overseas to France in October of 1917 during WWI. He died on the front lines on October 14, 1918 in Brieulles-sur-Meuse, France, when a shell crashed into the shack where he was sleeping.

His tombstone is engraved with the title 1st Lieutenant, the rank he held at his death. His family was unaware he was promoted to 1st Lieutenant until his twin brother, Sumner, visited Herbert's grave site.

The physical location of the grave is unknown. He was either buried in Brieulles-sur-Meuse or Meuse-Argonne American Cemetery.